Semiconductor integrated circuit device and process for manufacturing the same

ABSTRACT

A SRAM of complete CMOS type having its memory cell composed of six MISFETs, in which a pair of local wiring lines for connecting the input/output terminals of CMOS inverters are formed of a refractory metal silicide layer formed over a first conducting layer constituting the individual gate electrodes of the drive MISFETs, the transfer MISFETs and the load MISFETs of the memory cell and in which a reference voltage line formed over the local wiring lines is arranged to be superposed over the local wiring lines to form a capacity element. Moreover, the capacity element is formed between the local wiring lines and the first conducting layer by superposing the local wiring lines over the first conducting layer. Moreover, the local wiring lines are formed by using resistance lowering means such as silicification. In addition, there are made common the means for lowering the resistance of the gate electrode of the transfer MISFETs and the means for forming the local wiring lines.

This application is a Continuation application of application Ser. No.11/834,095, filed Aug. 6, 2007 now U.S. Pat. No. 7,511,377, which is aContinuation application of application Ser. No. 11/826,491, filed Jul.16, 2007 now U.S. Pat. No. 7,456,486, which is a Continuationapplication of application Ser. No. 11/765,265, filed Jun. 19, 2007 nowU.S. Pat. No. 7,397,123, which is a Divisional application ofapplication Ser. No. 11/297,500, filed Dec. 9, 2005, now U.S. Pat. No.7,253,051, issued Aug. 7, 2007, which is a Continuation application ofapplication Ser. No. 10/971,073, filed Oct. 25, 2004, now U.S. Pat. No.7,049,680, issued May 23, 2006, which is a Divisional application ofapplication Ser. No. 10/866,874, filed Jun. 15, 2004, now U.S. Pat. No.7,023,071, issued Apr. 4, 2006, which is a Continuation application ofapplication Ser. No. 10/304,045, filed Nov. 26, 2002, now U.S. Pat. No.6,809,399, issued Oct. 26, 2004, which is a Continuation application ofapplication Ser. No. 09/755,184, filed Jan. 8, 2001, now U.S. Pat. No.6,548,885, issued Apr. 15, 2003, which is a Divisional application ofapplication Ser. No. 09/334,266, filed Jun. 16, 1999, now U.S. Pat. No.6,211,004, issued Apr. 3, 2001, which is a Divisional application ofapplication Ser. No. 08/880,736, filed Jun. 23, 1997, now U.S. Pat. No.5,946,565, issued Aug. 31, 1999, which is a Continuation application ofapplication Ser. No. 08/451,117, filed May 25, 1995, now U.S. Pat. No.5,754,467, issued May 19, 1998, the contents of application Ser. No.08/451,117 being incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor integrated circuitdevice and a technique for manufacturing the same and, moreparticularly, to a technique which is effective if applied to asemiconductor integrated circuit device having a SRAM (i.e., StaticRandom Access Memory).

The SRAM, as acting as a semiconductor memory device, is equipped withmemory cells a memory cell which is disposed at an intersection betweena word line and a pair of complementary data lines and composed of aflip-flop circuit and two transfer MISFETs (i.e., Metal InsulatorSemiconductor Field Effect Transistors).

The flip-flop circuit of the memory cell of the SRAM is constructed asan information storage unit for storing information of 1 bit. Thisflip-flop circuit of the memory cell is exemplified by a pair of CMOS(i.e., Complementary metal Oxide Semiconductor) inverters. Each of theCMOS inverters is composed of n-channel type drive MISFETs and p-channelload MISFETs. On the other hand, transfer MISFETs are of the n-channeltype. In short, this memory cell is of the so-called “CMOS (i.e., FullComplementary Metal Oxide Semiconductor)” using the six MISFETs.Incidentally, the complete CMOS type SRAM, which is formed over theprincipal surface of the semiconductor substrate with the drive MISFETs,the load MISFETs and the transfer MISFETs, will be called the “bulk CMOStype SRAM”. This bulk CMOS type SRAM is disclosed, for example, on pp.590 to 593 of IEDM (i.e., International Electron Device Meeting),Technical Digest, 1985.

In the SRAM of this kind, the paired CMOS inverters constituting theflip-flop circuit have their input/output terminals crossly connectedwith each other through a pair of wiring lines (as will be called the“local wiring lines”). One of the CMOS inverters has its input/outputterminals connected with the source region of one of the transferMISFETs, and the other CMOS inverter has its input/output terminalsconnected with the source region of the other transfer MISFET. One ofthe complementary data lines is connected with the drain region of oneof transfer MISFETs, and the other complementary data line is connectedwith the drain region of the other transfer MISFET. With the individualgate electrodes of the paired transfer MISFETs, there is connected wordlines, by which are controlled the ON/OFF of the transfer MISFETs. Inthe above-specified Publication, the local wiring lines are formed by aself-aligning silicide process. This silicide process per se isdisclosed on pp. 118 to 121 of IEDM, Technical Digest, 1984.

SUMMARY OF THE INVENTION

As the capacity of a semiconductor memory device grows larger and largeraccording to the progress of the miniaturizing technique in recentyears, the area to be occupied by the memory cell of the aforementionedbulk CMOS type SRAM grows smaller and smaller. However, when the areaoccupied by the memory cell is reduced, the storage node capacity (i.e.,the pn junction capacity or gate capacity parasitic to theaforementioned storage nodes A and B) of the memory cell is reduced toreduce the amount of stored charge.

As a result, the resistance to the information inversion (i.e., theso-called “α ray soft error”) of the memory cell due to the α ray havingirradiated the surface of the semiconductor chip is lowered to make itdifficult to retain the safe operation of the memory cell. In order topromote the miniature structure without deteriorating the stableoperation of the memory cell, therefore, the counter-measures forretaining the amount of stored charge are indispensable.

More specifically, if the memory cell is irradiated with the a ray whichis emitted when a radioactive element, as contained in a trace amount ina package or resin material used for sealing the memory cell, such asuranium or thorium disintegrates, electron/hole pairs are produced alongthe range of the a ray to immigrate into the pn junction forming thestorage node so that the information of the memory cell is broken. Thisphenomenon is called the “soft error”. In the bulk CMOS type SRAM of theprior art, because of the large memory cell area, the capacity of thestorage node itself, as composed of a pn junction capacity or a gatecapacity, and the driving ability of the load MISFETs is so high thatthe storage node can be stored with charge sufficient for compensatingthe charge loss due to the α ray. If the memory cell area isminiaturized, however, the amount of charge to be stored in the storagenode is also reduced to raise a problem that the resistance of thememory cell to the irradiation of the α ray is deteriorated.

Specifically, we have found that new counter-measures for retaining thecharge storing amount of the memory cell is indispensable in the bulkCMOS type SRAM, too, for further miniaturizing the memory cell of theSRAM.

An object of the present invention is to provide a technique capable ofimproving the resistance to the soft error by increasing the storagenode capacity of the memory cell of the SRAM.

Another object of the present invention is to provide a techniquecapable of miniaturizing the memory cell of the SRAM.

Another object of the present invention is to provide a techniquecapable of operating the memory cell of the SRAM at a high speed and ata low voltage.

Another object of the present invention is to provide a techniquecapable of improving the production yield and reliability of the memorycell of the SRAM.

The foregoing and other objects and novel features of the presentinvention will become apparent from the following description to be madewith reference to the accompanying drawings.

The representative ones of the invention to be disclosed herein will besummarized in the following.

-   (1) A semiconductor integrated circuit device including a SRAM    having a memory cell comprising: a flip-flop circuit composed of a    pair of CMIS inverters having drive MISFETs and load MISFETs; and a    pair of transfer MISFETs connected with a pair of input/output    terminals of said flip-flop circuit, wherein a first conducting    layer is formed over the principal surface of a semiconductor    substrate to form the individual gate electrodes of said drive    MISFETs, said load MISFETs and said transfer MISFETs, wherein a    second conducting layer is formed over said first conducting layer    to form a pair of local wiring lines for connecting the individual    input/output terminals of said paired CMIS inverters, wherein a    third conducting layer is formed over said second conducting layer    to form a reference voltage line to be connected with the source    region of said drive MISFETs, and wherein said reference voltage    line is arranged to be superposed over said paired local wiring    lines.-   (2) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein said local wiring lines are partially extended over    the gate electrode of said drive MISFETs, said load MISFETs or said    transfer MISFETs.-   (3) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein said local wiring lines are partially extended over    a semiconductor region constituting the input/output terminals of    said CMIS inverters.-   (4) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein there is formed over said reference voltage line a    fourth conducting layer which is made of a conducting material    having a lower resistance than that of said third conducting layer    constituting said reference voltage line, for supplying a reference    voltage, and wherein said fourth conducting layer and said reference    voltage line are electrically connected through at least one    connection hole which is formed in each memory cell.-   (5) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein the connection hole for connecting said fourth    conducting layer and said reference voltage line and the connection    hole for connecting the reference voltage line and the source region    of said drive MISFETs are spaced from each other.-   (6) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein said local wiring lines are made of a refractory    metal silicide film.-   (7) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein the refractory metal silicide layer of said second    conducting layer is formed over the drain region of said transfer    MISFETs, wherein a pad layer of said third conducting layer is    formed over said refractory metal silicide layer, and wherein a data    line is connected with said drain region through said pad layer and    said refractory metal silicide layer.-   (8) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein the refractory metal silicide layer of said second    conducting layer is formed over the source region of said load    MISFETs, wherein a pad layer of said third conducting layer is    formed over said refractory metal silicide layer, and wherein a    reference voltage is supplied to said drain region through said pad    layer and said refractory metal silicide layer.-   (9) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein a well energizing semiconductor region having a    conduction type different from that of said source region is formed    over the principal surface of the semiconductor substrate adjacent    to the source region of said load MISFETs.-   (10) In the aforementioned SRAM, a semiconductor integrated circuit    device, wherein the gate electrode of said transfer MISFETs is made    of a conducting layer lying over said first conducting layer in    place of means made of said first conducting layer.-   (11) In a SRAM having a memory cell comprising: a flip-flop circuit    composed of a pair of CMOS inverters having drive MISFETs and load    MISFETs; and a pair of transfer MISFETs connected with a pair of    input/output terminals of said flip-flop circuit, a semiconductor    integrated circuit device wherein a first conducting layer is formed    over the principal surface of a semiconductor substrate to form the    individual gate electrodes of said drive MISFETs, said load MISFETs    and said transfer MISFETs, wherein a second conducting layer is    formed over said first conducting layer to form a pair of local    wiring lines for connecting the individual input/output terminals of    said paired CMOS inverters, wherein a third conducting layer is    formed over said second conducting layer to form a supply voltage    line to be connected with the source region of said load MISFETs,    and wherein said supply voltage line is arranged to be superposed    over said paired local wiring lines.-   (12) A process for manufacturing a semiconductor integrated circuit    device having wiring lines for connecting a first semiconductor    region of a first conduction type and a second semiconductor region    of a second conduction type, which are formed over a semiconductor    substrate at a spacing from each other, comprising the following    steps (a) to (d):-   (a) the step of selectively forming a first silicon layer on the    individual surfaces of said first semiconductor region and said    second semiconductor region;-   (b) the step of forming a refractory metal film all over the surface    of the semiconductor substrate, as covers said first silicon layer;-   (c) the step of patterning a second silicon layer into the shape of    said wiring lines after said second silicon layer is formed over    said refractory metal film; and-   (d) the step of thermally treating said semiconductor substrate to    silicify said first silicon layer, said refractory metal film and    said second silicon layer, and then removing said refractory metal    film left unreacted over said semiconductor substrate.-   (13) In a process for manufacturing a SRAM having a memory cell    comprising: a flip-flop circuit composed of a pair of CMIS inverters    having drive MISFETs and load MISFETs; and a pair of transfer    MISFETs connected with a pair of input/output terminals of said    flip-flop circuit, a process for manufacturing a semiconductor    integrated circuit device, wherein a pair of local wiring lines for    connecting the input/output terminals of said paired CMIS inverters    with each other are formed by the following steps (a) to (d):-   (a) the step of selectively forming a first silicon layer on the    individual surfaces of a first semiconductor region of a first    conduction type and a second semiconductor region of a second    conduction type, which constitute the input/output terminals of said    CMIS inverters, and on the partial surfaces of the individual gate    electrodes of said drive MISFETs and said load MISFETs;-   (b) the step of forming a refractory metal film all over the surface    of a semiconductor substrate, as covers said first silicon layer;-   (c) the step of patterning a second silicon layer into the shape of    local wiring lines after said second silicon layer is formed over    said refractory metal film; and-   (d) the step of thermally treating said semiconductor substrate to    silicify said first silicon layer, said refractory metal film and    said second silicon layer and then removing said refractory metal    film left unreacted over said semiconductor substrate.-   (14) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, further comprising,    before said step (a): the step of removing the thick insulating film    covering the portions of the individual gate electrodes of said    drive MISFETs and said load MISFETS, by the dry etching method using    a photoresist as the mask; and the step of removing the thin    insulating film, which covers the individual surfaces of said first    semiconductor region and said semiconductor region, by etching back    the entire surface of said semiconductor substrate, while leaving    said thin insulating film on the side walls of said gate electrode.-   (15) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein the    refractory metal silicide layer formed on the individual surfaces of    said first semiconductor region and said second semiconductor region    has a higher bottom face than the top face of the gate insulating    film of said drive MISFETs and said load MISFETs.-   (16) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein when said    second silicon layer is not left, when patterned at said step (c)    into the shape of said local wiring lines, on at least a portion of    such one of the individual semiconductor regions of said drive    MISFETs and said load MISFETs as does not constitute the    input/output terminals of said CMIS inverters.-   (17) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein a reference    voltage line or a supply voltage line is formed over said local    wiring lines after said step (d), and wherein a capacity is formed    between said local wiring lines and said reference voltage line or    said supply voltage line.-   (18) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein the second    silicon layer, as formed over said refractory metal film at said    step (c), is made thicker than the thickness necessary for said    silification.-   (19) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein a second    refractory metal film or its silicide film is formed over said    second silicon layer after said second silicon layer is formed over    said refractory metal film at said step (c).-   (20) In a process for manufacturing said SRAM, a semiconductor    integrated circuit device manufacturing process, wherein a    refractory metal silicide film is formed simultaneously with said    local wiring line forming step on such one of the individual    semiconductor regions of said drive MISFETs, said transfer MISFETs    and said load MISFETs as is connected with any of said data line,    said supply voltage line and said reference voltage line.

According to the aforementioned means (1), (11) and (17), the referencevoltage line to be formed over the local wiring lines is arranged to besuperposed over the local wiring lines so that the capacity element isformed between the reference voltage line and the local wiring lines. Asa result, the capacity of the storage nodes, as connected with the localwiring lines, can be increased to improve the resistance of the memorycell to the α ray soft error.

According to the aforementioned means (2), the local wiring lines arearranged to be partially superposed over the gate electrodes of thedrive MISFETs, the load MISFETs or the transfer MISFETs so that the gatecapacity component of the storage node capacity can be increased. As aresult, the storage node capacity of the memory cell can be increased toimprove the resistance to the a ray soft error.

According to the aforementioned means (3), the local wiring lines arearranged to be partially superposed over the storage nodes of the memorycell so that the capacity component of the diffusion layer of thestorage node capacity can be increased. As a result, the storage nodecapacity of the memory cell can be increased to improve the resistanceto the α ray soft error.

According to the aforementioned means (4), over the reference voltageline, there is arranged the wiring line having a lower resistance, andthe electric power is supplied from the lower-resistance wiring line tothe reference voltage through the connection holes which are formed inat lest one in each memory cell. As a result, the electric power of thereference voltage line can be supplied to each memory cell so that thereference voltage can be stabilized. As a result, the minimum value(V_(cc.min)) of the supply voltage can be improved to improve theresistance of the memory cell to the α ray soft error.

According to the aforementioned means (5), the connection holes forconnecting the lower-resistance wiring line and the reference voltageline and the connection holes for connecting the reference voltage lineand the source region of the drive MISFETs are spaced from each other sothat the step, which might otherwise be formed by the overlap of thoseconnection holes, can be avoided to flatten the connection hole formingregions. As a result, the connection holes can have their contactresistances reduced to operate the memory cell at a high speed and at alow voltage.

According to the aforementioned means (12) and (13), the local wiringlines are formed by causing the silicifying reaction among thepolycrystalline silicon film, the refractory metal film deposited on theformer, and the second polycrystalline silicon film deposited on theformer, so that the silicon in the semiconductor regions forming thestorage nodes of the memory cell can be prevented from participating inthe aforementioned silicifying reaction. As a result, the junctionleakage current of the semiconductor regions can be reduced to improvethe operational reliability of the memory cell.

According to the aforementioned means (14), the step of forming theconnection holes in the portions of the gate electrodes and the step ofexposing the semiconductor regions are carried out separately of eachother to make the allowance unnecessary for the mask alignment betweenthe connection holes and the semiconductor regions, so that the areasfor the connection holes can be reduced to highly integrate the memorycell. By connecting the local wiring lines and the semiconductor regionsin self-alignment, moreover, no allowance is required for the maskalignment of the two so that the memory cell size can be reduced tohighly integrate the memory cell.

According to the aforementioned means (6), (12) and (13), the pairedlocal wiring lines for connecting the storage nodes of the memory cellare made of the refractory metal silicide, so that the p-type impurityin the semiconductor region of the load MISFETs and the n-type impurityin the semiconductor region or the gate electrodes of the drive MISFETscan be prevented from diffusing into each other through the local wiringlines. As a result, the ohmic connections can be made with a lowresistance between the semiconductor regions of the different conductiontypes and between the semiconductor region and the gate electrodesthereby to operate the memory cell at a high speed and at a low voltage.

According to the aforementioned means (15), even in the case of amisalignment of the photoresist to be used as the mask at the time ofetching the overlying polycrystalline silicon film, it is possible toprevent the underlying polycrystalline silicon film from being scraped.As a result, the allowance for the alignment of the photoresist can beeliminated to reduce the areas for the semiconductor regions thereby tohighly integrate the memory cell.

According to the aforementioned means (7), (8) and (20), the refractorymetal silicide layers are formed on the surfaces of at least theportions of the individual source regions and drain regions of thetransfer MISFETs, the drive MISFETs and the load MISFETs, asconstituting the memory cell, so that the source regions and the drainregions can have their resistances lowered. As a result, it is possibleto operate the memory cell at a high speed and at a low voltage.

According to the aforementioned means (9), the source region, the wellenergizing drain region and the supply voltage line can be ohmicallyconnected without considering the conduction type of the polycrystallinesilicon pad layer, as formed on the refractory metal silicide layer, sothat the source region and the well energizing drain region of the loadMISFETs can be simultaneously supplied with the supply voltage throughthe one connection hole. As a result, the source region and the wellenergizing drain region of the load MISFETs can be arranged adjacent toeach other and can have their areas reduced to highly integrate thememory cell.

According to the aforementioned means (18), when the local wiring linesare to be formed by the silicifying reaction, their thickness andsurface areas are increased by making the polycrystalline silicon film,as deposited on the refractory metal silicide layer, thicker than thatnecessary for that silicifying reaction, so that the capacity to beestablished between the local wiring lines and the overlying referencevoltage line is increased. As a result, the storage node capacity of thememory cell can be further increased to improve the resistance to thearray soft error.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing a memory cell of a SRAM according to afirst embodiment of the present invention;

FIG. 2 is a section showing an essential portion of a semiconductorsubstrate taken along line II-II′ of FIG. 1;

FIG. 3 is an equivalent circuit diagram of the memory cell of the SRAMof the present invention;

FIG. 4 is a top plan view showing the super-position of the local wiringlines and the gate electrodes of the memory cell of the SRAM of thepresent invention;

FIG. 5 is a top plan view showing the superposition of the local wiringlines and the storage nodes of the memory cell of the SRAM of thepresent invention;

FIG. 6 is a top plan view showing the super-position of the local wiringlines and the reference voltage line of the memory cell of the SRAM ofthe present invention;

FIG. 7 is a perspective view showing the superposition of the localwiring lines and the reference voltage line of the memory cell of theSRAM of the present invention;

FIG. 8 is a section of an essential portion of a semiconductor substrateand shows a process for manufacturing the memory cell of the SRAM of thepresent invention;

FIG. 9 is a top plan view showing the active region of the memory cellof the SRAM of the present invention;

FIG. 10 is a top plan view showing the active region patterns for thesixteen memory cells of the SRAM of the present invention;

FIG. 11 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 12 is a top plan view of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 13 is a top plan view showing a gate electrode (or word line)pattern for the sixteen memory cells of the SRAM of the presentinvention;

FIG. 14 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 15 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 16 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 17 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 18 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 19 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 20 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 21 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 22 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 23 is a top plan view of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 24 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 25 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 26 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 27 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 28 is a top plan view of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 29 is a top plan view showing the local wiring line pattern for thesixteen memory cells of the SRAM of the present invention;

FIG. 30 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 31 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 32 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 33 is a top plan view of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 34 is a top plan view showing the reference voltage line patternfor the sixteen memory cells of the SRAM of the present invention;

FIG. 35 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 36 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 37 is a top plan view of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 38 is a top plan view showing the data line pattern for the sixteenmemory cells of the SRAM of the present invention;

FIG. 39 is a section of an essential portion of the semiconductorsubstrate and shows a process for manufacturing the memory cell of theSRAM of the present invention;

FIG. 40 is a section of an essential portion of the semiconductorsubstrate and shows another process for manufacturing the memory cell ofthe SRAM of the present invention;

FIG. 41 is a top plan view of an essential portion of the semiconductorsubstrate and shows another construction of the memory cell of the SRAMof the present invention;

FIG. 42 is a top plan view of an essential portion of the semiconductorsubstrate and shows another construction of the memory cell of the SRAMof the present invention;

FIG. 43 is a top plan view of an essential portion of the semiconductorsubstrate and shows another construction of the memory cell of the SRAMof the present invention;

FIG. 44 is a top plan view showing a semiconductor integrated circuitdevice according to a second-embodiment of the present invention;

FIG. 45 is a top plan view showing the semiconductor integrated circuitdevice according to the second embodiment of the present invention;

FIG. 46 is a top plan view showing the semiconductor integrated circuitdevice according to the second embodiment of the present invention;

FIGS. 47( a), 47(b) and 47(c) are sections for explaining the steps ofmanufacturing the semiconductor integrated circuit device according tothe second embodiment of the present invention;

FIGS. 48( a), 48(b) and 48(c) are sections for explaining the steps ofmanufacturing the semiconductor integrated circuit device according tothe second embodiment of the present invention;

FIGS. 49( a), and 49(b) are sections for explaining the steps ofmanufacturing the semiconductor integrated circuit device according tothe second embodiment of the present invention;

FIG. 50 is a section showing a semiconductor integrated circuit deviceaccording to a third embodiment of the present invention;

FIG. 51 is a section showing a semiconductor integrated circuit deviceaccording to a fourth embodiment of the present invention;

FIG. 52 is a section showing a semiconductor integrated circuit deviceaccording to a fifth embodiment of the present invention;

FIG. 53 is a section showing a semiconductor integrated circuit deviceaccording to a sixth embodiment of the present invention;

FIG. 54 is a top plan view showing a semiconductor integrated circuitdevice according to a seventh embodiment of the present invention;

FIG. 55 is an equivalent circuit diagram showing the semiconductorintegrated circuit device according to the seventh embodiment of thepresent invention;

FIG. 56 is a top plan view showing the semiconductor integrated circuitdevice according to the seventh embodiment of the present invention;

FIG. 57 is a section showing a semiconductor integrated circuit deviceaccording to an eighth embodiment of the present invention;

FIG. 58 is a top plan view showing a semiconductor integrated circuitdevice according to a ninth embodiment of the present invention;

FIG. 59 is a top plan view showing a semiconductor integrated circuitdevice according to a tenth embodiment of the present invention;

FIGS. 60( a), 60(b) and 60(c) are sections for explaining the steps ofmanufacturing a semiconductor integrated circuit device according to aneleventh embodiment of the present invention;

FIGS. 61( a), 61(b) and 61(c) are sections for explaining the steps ofmanufacturing a semiconductor integrated circuit device according to aneleventh embodiment of the present invention;

FIG. 62 is a section showing a semiconductor integrated circuit deviceaccording to a twelfth embodiment of the present invention;

FIG. 63 is a section showing a semiconductor integrated circuit deviceaccording to a thirteenth embodiment of the present invention;

FIGS. 64( a) and 64(b) are sections showing the steps of manufacturingthe semiconductor integrated circuit device according to a fourteenthembodiment of the present invention;

FIGS. 65( a) and 65(b) are sections showing the steps of manufacturingthe semiconductor integrated circuit device according to a fourteenthembodiment of the present invention;

FIG. 66 is a section showing a semiconductor integrated circuit deviceaccording to a fifteenth embodiment of the present invention;

FIG. 67 is a section showing a semiconductor integrated circuit deviceaccording to a sixteenth embodiment of the present invention; and

FIG. 68 is a section showing a semiconductor integrated circuit deviceaccording to a seventeenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The present invention will be described in detail in the following inconnection with its embodiments with reference to the accompanyingdrawings. Incidentally, throughout Figures for describing theembodiments, the repeated description of the parts or portions havingidentical functions will be omitted by designating them at the samereference characters.

FIG. 1 is a top plan view showing a memory cell of a SRAM according tothe present embodiment, and

FIG. 2 is a section taken along line II-II′ of FIG. 1.

FIG. 3 is an equivalent circuit diagram of a memory cell of the SRAM ofthe present embodiment. As shown in FIG. 3, the memory cell of the SRAMof the present embodiment is composed of a pair of drive MISFETs Qd₁ andQd₂, a pair of load MISFETs Qp₁ and Qp₂ and a pair of transfer MISFETsQt₁ and Qt₂, which are arranged at an intersecting portion between apair of complementary data lines (i.e., data line DL and barred dataline DL) and a word line WL. The drive MISFETs Qd₁ and Qd₂ and thetransfer MISFETs Qt₁ and Qt₂ belong to the n-channel type whereas theload MISFETs Qp₁ and Qp₂ belong to the p-channel type. In short, thismemory cell belongs to the complete CMOS type (i.e., the bulk CMOS typeSRAM) composed of the four n-channel MISFETs and the two p-channelMISFETs.

Of these six MISFETs composing the memory cell, the drive MISFET Qd₁ andthe load MISFET Qp₁ constitute a CMOS inverter (INV₁), and the driveMISFET Qd₂ and the load MISFET Qp₂ constitute a CMOS inverter (INV₂).These paired CMOS inverters (INV₁ and INV₂) have their input/outputterminals (i.e., storage nodes A and B) crossly coupled through a pairof local wiring lines L₁ and L₂ to constitute a flip-flop acting as aninformation storage unit for storing information of 1 bit.

This flip-flop circuit has its one input/output terminal (i.e., thestorage node A) connected with the source region of the transfer MISFETQt₁ and its other input/output terminal (i.e. the storage node B)connected with the source region of the transfer MISFET Qt_(2.) Thetransfer MISFET Qt₁ has its drain region connected with the data lineDL, and the transfer MISFET Qt₂ has its drain region connected with thebarred data line DL.

Moreover, the flip-flop circuit has its one end (i.e., the sourceregions of the load MISFETs Qp₁ and Qp₂) connected with a supply voltage(Vcc) and its other end (i.e., the source regions of the drive MISFETsQd₁ and Qd₂) connected with a reference voltage (V_(ss)) The supplyvoltage (V_(cc)) is exemplified by 5 V, Land the reference voltage(V_(ss)) is exemplified by 0 V (i.e., the GND potential).

Here will be described the operations of the aforementioned circuit.When one CMOS inverter (INV₁) has its storage node A at a high (“H”)potential, the drive MISFET Qd₂ is turned ON whereas the load MISFET Qp₂is turned OFF, so that the other CMOS inverter (INV₂) has its storagenode B set to a low (“L”) potential. Moreover, the drive MISFET Qd₁ isturned OFF whereas the load MISFET Qp₁ is turned ON, so that the storagenode A is held at the high (“H”) potential. In other words, the statesof the mutual storage nodes A and B are latched by the latch circuithaving the paired CMOS inverters (INV₁ and INV₂) crossly connected, sothat the information is stored while the supply voltage is applied.

The transfer MISFETs Qt₁ and Qt₂ have their individual gate electrodesconnected with the word line WL, by which their ON and OFF arecontrolled. Specifically, when the word line WL is at the high (“H”)potential, the transfer MISFETs Qt₁ and Qt₂ are ON to electricallyconnect the latch circuit and the complementary data lines (i.e., thedata line DL and the barred data line DL) so that the potential state(i.e., “H” or “L”) of the storage nodes A and B appears on the data lineDL and the data line DL and is read as the information of the memorycell.

In order to write the information in the memory cell, the information ofthe data lines DL and barred DL is transmitted to the storage nodes Aand B by setting the word line WL to the “H” potential level and byturning ON the transfer MISFETs Qt₁ and Qt₂. In order to read theinformation of the memory cell, on the other hand, the information ofthe storage nodes A and B is transmitted to the data lines DL and DLlikewise by setting the word line WL to the “H” potential level and byturning ON the transfer MISFETs Qt₁ and Qt₂.

A specific construction of the aforementioned memory cell will bedescribed with reference to FIG. 1 (presenting a top plan view of asemiconductor substrate and showing about one memory cell), FIG. 2(presenting a section of the semiconductor substrate, as taken alongline II-II′ of FIG. 1) and FIGS. 3 to 7. Incidentally, FIG. 1 and FIGS.4 to 7 show only the conducting layers of the memory cell but not theinsulating films such as element isolating insulating films orinter-layer insulating films.

As shown in FIGS. 2 and 4, the six MISFETs composing the memory cell isformed in the active region which is surrounded by a field insulatingfilm of a p⁻-type semiconductor substrate 1. The drive MISFETs Qd₁ andQd₂ and the transfer MISFETs Qt₁ and Qt₂ of the n-channel type areindividually formed in the active region of a p-type well 3, and theload MISFETs Qp₁ and Qp₂ of the p-channel type are formed in the activeregion of an n-type well 4. The p-type well 3 and the n-type well 4 areindividually formed in the principal surface of a p-type epitaxialsilicon layer 5 formed over the semiconductor substrate 1.

The transfer MISFETs Qt₁ and Qt₂ have a gate electrode 6 integrated withthe word line WL. This gate electrode 6 (or the word line WL) is formedof a polycrystalline silicon film (or a poly-cide film having alamination of a polycrystalline silicon film and a refractory metalsilicide film) and is formed over a gate insulating film 7 made of asilicon oxide film.

The aforementioned transfer MISFETs Qt₁ and Qt₂ have their individualsource regions and drain regions formed of a lightly doped n⁻-typesemiconductor region 8 and a heavily doped n⁺-type semiconductor region9, which are formed in the active region of the p-type well 3. In short,the transfer MISFETs Qt₁ and Qt₂ have their individual source regionsand drain regions constructed of the LDD (i.e., Lightly Doped Drain)structure.

The drive MISFET Qd₁ and the load MISFET Qp₁, as constituting one CMOSinverter (INV₁) of the flip-flop circuit, have a common gate electrode10 a, and the drive MISFET Qd₂ and the load MISFET Qp₂, as constitutingthe other CMOS inverter (INV₂), have a common gate electrode 10 b. Thesegate electrodes 10 a and 10 b are made of the same polycrystallinesilicon film as that of the gate electrode 6 (or the word line WL) ofthe aforementioned transfer MISFETs Qt₁ and Qt₂ and are formed over thegate insulating film 7. The polycrystalline silicon film forming thegate electrode 6 (or the word line WL) and the gate electrodes 10 a and10 b is doped with an n-type impurity (e.g., phosphorous (P)).

The individual source regions and drain regions of the drive MISFETs Qd₁and Qd₂ are formed of the lightly doped n⁻-type semiconductor region 8and the heavily doped n⁺-type semiconductor region 9, which are formedin the active region of the p-type well 3, In short, the individualsource regions and drain regions of the drive MISFETs Qt₁ and Qd₂ areconstructed of the LDD structure. On the other hand, the individualsource regions and drain regions of the load MISFETs Qp₁ and Qp₂ areformed of a lightly doped p⁻-type semiconductor region 11 and a heavilydoped p⁺-type semiconductor region 12, which are formed in the activeregion of the n-type well 4. In short, the individual source regions anddrain regions of the load MISFETs Qp₁ and Qp₂ are constructed of the LDDstructure.

Over the aforementioned six MISFETs constituting the memory cell, thereare formed a pair of local wiring lines L₁ and L₂ through a siliconoxide insulating film 13 and a side wall insulating film (or side wallspacer) 14, which cover the upper portions of the gate electrodes (6, 10a and 10 b) and the side walls. These paired local wiring lines L₁ andL₂ are formed of a refractory metal silicide film, which is formed byreacting a polycrystalline silicon film and a refractory metal film overthe semiconductor substrate 1, such as a cobalt silicide (CoSi_(x))film. The paired local wiring lines L₁ and L₂ are formed inself-alignment with the side wall insulating film 14, as will bedescribed hereinafter. Moreover, the side wall insulating film 14 isformed in self-alignment with the gate electrodes (6, 10 a and 10 b).

One local wiring line L₁ is connected with the drain region (i.e., thep⁺-type semiconductor region 12) of the load MISFET Qp₁ and the drainregion (i.e., the n⁺-type semiconductor region 9) of the drive MISFETQd₁ and the gate electrode 10 b of the drive MISFET Qd₂ and with theload MISFET Qp₂ through connection holes 15 which are opened in theinsulating film 13. The other local wiring line L₂ is connected with thedrain region (i.e., the n⁺-type semiconductor region 9) of the loadMISFET Qp₂ and the drain region (i.e., the n⁺-type semiconductor region9) of the drive MISFET Qd₂ and with the gate electrode 10 a of the driveMISFET Qd₁ and the load MISFET Qp₁ through the connection holes 15 whichare opened in the insulating film 13.

The drain region (i.e., the n⁺-type semiconductor region 9) of thetransfer MISFET Qt₁ is formed on its surface with a refractory metalsilicide layer such as a cobalt silicide (CoSi) layer 16, and the drainregion (i.e., the n⁺-type semiconductor region 9) of the transfer MISFETQt₂ is formed on its surface with the same cobalt silicide layer 16.With the drain region of the transfer MISFETs Qt₁ and Qt₂, there areconnected the data lines DL and DL through the cobalt silicide layer 16.This cobalt silicide layer 16 is formed at the same step as that of thelocal wiring lines L₁ and L₂, as will be described hereinafter.

The source region (i.e., the p⁺-type semiconductor region 12) of theload MISFET Qp₁ and an n⁺-type semiconductor region 18, as formedadjacent to that source region, are formed thereover with a refractorymetal silicide layer such as a cobalt silicide layer 17. The sourceregion (i.e., the p⁺-type semiconductor region 12) of the load MISFETQp₂ and the n⁺-type semiconductor region 18, as formed adjacent to thatsource region, are also formed thereover with the same cobalt silicidelayer 17. The source region and the n⁺-type semiconductor region 18 ofthe load MISFETs Qp₁ and Qp₂ are individually supplied with the supplyvoltage (V_(cc)) through a later-described supply voltage line. Thecobalt silicide layer 17 is formed at the same step as that of the localwiring lines L₁ and L₂ and the cobalt silicide layer 16.

FIGS. 4 and 5 are top plan views showing the layout of theaforementioned paired local wiring lines L₁ and L₂ and their underlyinggate electrodes 10 a and 10 b.

As shown in FIG. 4, one local wiring line L₁ extends to have its portionsuperposed over the gate electrode 10 a, and the other local wiring lineL₂ extends to have its portion superposed over the gate electrode 10 b.Although not shown, however, the local wiring lines L₁ and L₂ may extendto have their portions superposed over the gate electrode 6 (i.e., theword line WL).

Thus, the memory cell of the SRAM of the present embodiment is arrangedsuch that the local wiring lines L₁ and L₂ are superposed as much aspossible over the gate electrode 10 a (of the drive MISFET Qd₁ and theload MISFET Qp₁), the gate electrode 10 b (of the drive MISFET Qd₂ andthe load MISFET Qp₂) or the gate electrode 6 (i.e., the word line WL)(of the transfer MISFETs Qt₁ and Qt₂). Thanks to this construction, agate capacity component (C₁) (as shown in FIG. 3) of the storage nodecapacity can be increased to increase the storage node capacity of thememory cell thereby to improve the resistance to an a ray soft error.Specifically, the gate electrodes 6, 10 a and 10 b, the silicon oxidefilms 13 and 14 and the local wiring lines L₁ and L₂ constitute thecapacity element C₁. The silicon oxide films 13 and 14 act as dielectricfilms of the capacity element C₁.

As shown by netted patterns in FIG. 5, moreover, one local wiring lineL₁ is extended partially over the semiconductor region (i.e., then⁺-type semiconductor region 9 of the drive MISFET Qd₁ and the p⁺-typesemiconductor region 12 of the load MISFET Qp₁) constituting the storagenode A of the memory cell, and the other local wiring line L₂ isextended partially over the semiconductor region (i.e., the n⁺-type 9 ofthe drive MISFET Qd₂ and the p⁺-type semiconductor region 12 of the loadMISFET Qp₂) constituting the storage node B of the memory cell.

In short, the memory cell of the SRAM of the present embodiment isarranged such that the local wiring lines L₁ and L₂ are partiallysuperposed over the storage nodes A and B of the memory cell. Thanks tothis construction, the capacity component of the diffusion layer of thestorage node capacity can be increased to increase the storage nodecapacity of the memory cell thereby to improve the resistance to the aray soft error.

Over the aforementioned local wiring lines L₁ and L₂, as shown in FIGS.2 and 6, there is formed a reference voltage line 20 through a thininsulating film 19 which is formed of a laminated film of a siliconoxide film and a silicon nitride film. This reference voltage line 20 isarranged to cover the local wiring lines L₁ and L₂. The referencevoltage line 20 is made of a polycrystalline silicon film doped with ann-type impurity (e.g., P) and is connected with the individual sourceregions (i.e., the n⁺-type semiconductor region 9) of the drive MISFETsQd₁ and Qd₂ through connection holes (as shown in FIG. 1) opened in theinsulating film 19 and an insulating film (identical to the gateinsulating film 7).

Over the drain region (i.e., the n⁺-type semiconductor region 9) of thetransfer MISFETs Qt₁ and Qt₂, there is formed a pad layer 22 which ismade of the same polycrystalline silicon film as that of theaforementioned reference voltage line 20. This pad layer 22 iselectrically connected with the aforementioned refractory metal silicidelayer 16 through connection holes 23 which are opened in the insulatingfilm 19. Over the individual source regions (i.e., the p⁺-typesemiconductor region 12) of the load MISFETs Qp₁ and Qp₂, there isformed a pad layer 24 which is made of the same polycrystalline siliconfilm as the aforementioned reference voltage line 20. This pad layer 24is electrically connected with the aforementioned refractory metalsilicide layer 17 through connection holes 25 opened in the insulatingfilm 19.

FIG. 6 is a top plan view showing the layout of the aforementionedreference voltage line 20 and the underlying local wiring lines L₁ andL₂, and FIG. 7 is a perspective view of the same.

As shown, the reference voltage line 20 is formed to cover substantiallyall over the local wiring lines L₁ and L₂. Specifically, the memory cellof the SRAM of the present embodiment is arranged such that thereference voltage line 20 formed over the local wiring lines L₁ and L₂is superposed over the local wiring lines L₁ and L₂. Thanks to thisconstruction, the reference voltage line 20, the local wiring lines L₁and L₂ and the thin insulating film (i.e., the dielectric film) 19sandwiching former constitute a capacity element (C₂) so that thecapacity of the storage nodes A and B connected with the local wiringlines L₁ and L₂ can be increased to improve the resistance of the memorycell to the α ray soft error.

Over the aforementioned reference voltage line 20, as shown in FIGS. 1and 2, there is formed a first-layered metal wiring line through aninter-layer insulating film 26. This inter-layer insulating film 26 isformed of a laminated film of a silicon oxide film and a BPSG (i.e.,Boro Phospho Silicate Glass) film. The first-layered metal wiring lineis made of an aluminum (Al) alloy, for example, to constitute a supplyvoltage line 27, a sub-reference voltage line 28, a sub-word line (or adivided word line) 29 and a pad layer 30.

The supply voltage line 27 is electrically connected with theaforementioned pad layer 24 through connection holes 31 opened in theinter-layer insulating film 26. The sub-reference voltage line 28 iselectrically connected with the reference voltage line 20 throughconnection holes 32 (as shown in FIG. 1) opened in the inter-layerinsulating film 26. The sub-word line 29 is electrically connected withthe aforementioned word line WL through the (not-shown) connection holesopened in the inter-layer insulating film 26 and the insulating films 19and 13. The pad layer 30 is electrically connected with theaforementioned pad layer 22 through connection holes 33 opened in theinter-layer insulating film 26.

Thus, in the memory cell of the SRAM of the present embodiment, thereference voltage line 20, as made of a polycrystalline silicon film, isoverlaid by the sub-reference voltage line 28, which is made of Alhaving a lower resistance than polycrystalline silicon, and is suppliedwith the electric power from the sub-reference voltage line 28 throughthe connection holes 32, at least one of which is formed in each memorycell. Thanks to this construction, the reference voltage (V_(ss)) can besupplied to each memory cell so that it can be stabilized. As a result,the supply voltage (V_(cc)) can have its minimum value (V_(cc.min))increased to improve the resistance of the memory cell to the α ray softerror.

In the memory cell of the SRAM of the present embodiment, as shown inFIG. 1, the aforementioned connection hole 32 for connecting thesub-reference voltage line 28 and the reference voltage line 20 and theaforementioned connection hole 21 for connecting the reference voltageline 20 and the source region (i.e., the n⁺-type semiconductor region 9)of the drive MISFETs Qd₁ and Qd₂ are arranged at a spacing from eachother. Thanks to this construction, the step, which might otherwise beformed by the overlap of the connection holes 21 and 32, can be avoidedto flatten the connection forming regions so that the contactresistances of the connection holes 21 and 32 can be reduced to operatethe memory cell at a high speed and at a low voltage.

The aforementioned first-layered metal wiring line is overlaid by thesecond-layered metal wiring line through an inter-layer insulating film34. This inter-layer insulating film 34 is formed of a three-layeredfilm which is composed of a silicon oxide film 34 a, a spin-on-glassfilm 34 b and a silicon oxide film 34 c sequentially in the recitedorder from the lower-most layer. The second-layered metal wiring line ismade of an aluminum alloy, for example, to constitute the aforementioneddata lines DL and DL. These data lines DL and DL are electricallyconnected with the aforementioned pad layer 30 through connection holes35 which are opened in the inter-layer insulating film 34.

Here will be described a process for manufacturing the memory cell ofthe SRAM of the present embodiment thus constructed. Incidentally, thesections of the Figures (i.e., FIGS. 8 to 39) showing the memory cellmanufacturing method are taken along line II-II′ of FIG. 1. On the otherhand, the top plan views show only the conducting layers, and theinsulating films between the individual conducting layers are not shown.First of all, the p-type epitaxial silicon layer 5 is made to grow onthe semiconductor substrate 1 made of p⁻-type single crystal silicon, asshown in FIG. 8. After this, the field insulating film 2, as made of athick silicon oxide film, is formed on the surface of the epitaxialsilicon layer 5 by the well-known LOCOS method using a silicon nitridefilm as the thermal oxidation mask. Subsequently, the epitaxial siliconlayer 5 is doped with an n-type impurity (P) and a p-type impurity (BF₂)by the ion implantation method using a photoresist as the mask. Afterthis, these impurities are extended and diffused to form the p-type well3 and the n-type well 4. Next, these p-type well 3 and n-type well 4, asenclosed by the field insulating film 2, are formed on their individualprincipal surfaces with the gate insulating film 7 made of a thinsilicon oxide film having a thickness as small as about 9 nm.

FIG. 9 is a top plan pattern of an active region AR (of one memory cell)enclosed by the aforementioned field insulating film 2. The memory cellis formed in the rectangular region which is defined by the four “+”symbols in FIG. 9. This memory cell has its size exemplified by about4.0 (μm)×2.8 (μm). Moreover, the pattern of the active pattern AR of thesixteen memory cells is shown in FIG. 10.

Next, the gate electrode 6 (i.e., the word line WL) of the transferMISFETs Qt₁ and Qt₂ and the gate electrodes 10 a and 10 b of the driveMISFETs Qt₁ and Qd₂ and the load MISFETs Qp₁ and Qp₂ are formed, asshown in FIGS. 11 and 12. The gate electrode 6 (or the word line WL) andthe gate electrodes 10 a and 10 b are formed, for example, by depositinga polycrystalline silicon film having a thickness of about 100 nm allover the semiconductor substrate 1 by the CVD (i.e., Chemical VaporDeposition) method, subsequently by depositing the insulating film 13 ofsilicon oxide (having a thickness of about 120 nm) by the CVD method,and by patterning the insulating film 13 and the polycrystalline siliconfilm by the dry etching method. FIG. 13 shows a pattern of the gateelectrodes 6 (i.e., the word lines WL) and the gate electrodes 10 a and10 b for the sixteen memory cells.

Next, the p-type well 3 and the n-type well 4 are partially doped withn-type impurities (phosphorous (P) and arsenic (As)) by the ionimplantation using a photoresist PL1 as the mask, as shown in FIG. 14.Next, the photoresist PL1 is removed, and the n-type well 4 is dopedwith a p-type impurity (e.g., boron fluoride (BF₂)) by the ionimplantation method using a photoresist PL2 as the mask, as shown inFIG. 15. Next, the photoresist PL2 is removed, the silicon oxide film,as deposited all over the semiconductor substrate 1 by the CVD method,is patterned by the RIE (i.e., Reactive Ion Etching) method, forexample, the side wall insulating film (i.e., the side wall spacer) 14in self-alignment with the side walls of the gate electrode 6 (i.e., theword line WL) and the gate electrodes 10 a and 10 b, as shown in FIG.16.

Next, the p-type well 3 and the n-type well 4 are partially doped withan n-type impurity (P and As) by the ion implantation using aphotoresist PL3 as the mask. Next, the photoresist film PL3 is removed,and the n-type well 4 is doped with a p-type impurity (BF₂) by the ionimplantation method using a photoresist PL4 as the mask, as shown inFIG. 18.

Next, the photoresist PL4 is removed, and the n-type impurity and thep-type impurity are thermally diffused to form the principal surface ofthe p-type well 3 with the individual source region and drain region(i.e., the n⁻-type semiconductor region 8 and the n⁺-type semiconductorregion 9) of the transfer MISFETs Qt₁ and Qt₂ and the drive MISFETs Qd₁and Qd₂ and the principal surface of the n-type well 4 with the sourceregion and drain region (i.e., the p⁻-type semiconductor region 11 andthe p⁺-type semiconductor region 12) of the load MISFETs Qp₁ and Qp₂, asshown in FIG. 19.

Next, the insulating film 14, as covering the gate electrodes 10 a and10 b of the drive MISFETs Qd₁ and Qd₂, is formed with the connectionhole 15 by the dry etching method using a photoresist PL5 as the mask,as shown in FIG. 20, to partially expose the gate electrodes 10 a and 10b.

Next, the photoresist PL5 is removed, and the semiconductor substrate 1is etched back all over its surface to remove the insulating film (i.e.,the same insulating film as the gate insulating film 7) covering theindividual surfaces of the individual source and drain region (i.e., then⁺-type semiconductor region 9) of the drive MISFETs Qd₁ and Qd₂ and thetransfer MISFETs Qt₁ and Qt₂, the source region and drain region (i.e.,the p⁺-type semiconductor region 12) of the load MISFETs Qp₁ and Qp₂,and the well energizing n⁺-type semiconductor region 18, thereby toexpose the n⁺-type semiconductor region 9, the p⁺-type semiconductorregion 12 and the n⁺-type semiconductor region 18.

Thus, in the manufacture process of the present embodiment, theinsulating film 13 over the gate electrodes 10 a and 10 b is formed atfirst with the connection hole 15 by the dry etching method using thephotoresist PL5 as the mask, and the semiconductor substrate 1 is thenetched all over the surface to remove the insulating film covering theindividual surfaces of the n⁺-type semiconductor region 9, the p⁺-typesemiconductor region 12 and the n⁺-type semiconductor region 18.

In other words, the step of partially exposing the gate electrodes 10 aand 10 b and the step of exposing the n⁺-type semiconductor region 9,the p⁺-type semiconductor region 12 and n⁺-type semiconductor region 18are executed separately of each other to expose the n⁺-typesemiconductor region 9, the p⁺-type semiconductor region 12 and then⁺-type semiconductor region 18 in self-alignment with the side wallinsulating film 14. Thanks to this construction, no mask allowance isrequired for the connection hole 15 with the n⁺-type semiconductorregion 9, the p⁺-type semiconductor region 12 and the n⁺-typesemiconductor region 18 so that the areas for the connection hole 15,the n⁺-type semiconductor region 9, the p⁺-type semiconductor region 12and the n⁺-type semiconductor region 18 can be reduced to highlyintegrate the memory cell.

Incidentally, in case the mask alignment is allowed, the aforementionedmeans may be replaced by the dry etching method using a photoresist asthe mask to simultaneously expose the portions of the gate electrodes 10a and 10 b, the n⁺-type semiconductor region 9, the p⁺-typesemiconductor region 12 and n⁺-type semiconductor region 18. In thiscase, the aforementioned etching-back step is not necessary so that themanufacture process for the memory cell can be shortened.

Next, as shown in FIGS. 22 and 23, a thin polycrystalline silicon film36 having a thickness of about 40 nm is selectively deposited by theselective CVD method over the individual surfaces of the portions of thegate electrodes 10 a and 10 b, the n⁺-type semiconductor region 9, thep⁺-type semiconductor region 12 and the n⁺-type semiconductor region 18,which are exposed by the aforementioned step. In other words, thepolycrystalline silicon film 36 is deposited only on the gate electrodes10 a and 10 b, the n⁺-type semiconductor region 9, the p⁺-typesemiconductor region 12 and the n⁺-type semiconductor region 18 but notonly the insulating films 13 and 14 made of a silicon oxide film.Alternatively, the polycrystalline silicon film 36 may be left on theindividual surfaces of the portions of the gate electrodes 10 a and 10b, the n⁺-type semiconductor region 9, the p⁺-type semiconductor region12 and the n⁺-type semiconductor region 18 by depositing thepolycrystalline silicon film 36 on the entire surface of thesemiconductor substrate 1 and by patterning the polycrystalline siliconfilm 36 by the dry etching method using the photoresist as the mask.

Next, as shown in FIG. 24, a thin Co film 37 having a thickness of about20 nm is deposited all over the surface of the semiconductor substrate 1by the sputtering method, an; as shown in FIG. 25, a thinpolycrystalline silicon film 38 having a thickness of about 40 nm isthen deposited all over the surface of the semiconductor substrate 1 bythe CVD method or the sputtering method. Thus, according to themanufacture process of the present embodiment, the polycrystallinesilicon film 36, the Co film 37 and the polycrystalline silicon film 38are deposited on the individual surfaces of the portions of the gateelectrodes 10 a and 10 b, the n⁺-type semiconductor region 9, thep⁺-type semiconductor region 12 and the n⁺-type semiconductor region 18,whereas the Co film 37 and the polycrystalline silicon film 38 aredeposited on the remaining regions (e.g., the insulating film).Incidentally, in place of the aforementioned Co film 37, there may bedeposited another refractory metal film such as a thin film of W(tungsten), Mo (molybdenum), Ti (titanium) or Ta (tantalum).

Next, as shown in FIG. 26, the overlying polycrystalline silicon film 38is patterned by the dry etching method using a photoresist 39 so that itis left on the individual surfaces of the region to be formed with thelocal wiring lines L₁ and L₂, the drain region (i.e., the n⁺-typesemiconductor region 9) of the transfer MISFETs Qt₁ and Qt₂, the sourceregion (i.e., the p⁺-type semiconductor region 12) of the load MISFETsQp₁ and Qp₂, and the n⁺-type semiconductor region 9 adjacent to theformer.

The photoresist 39 acting as the etching mask of the aforementionedpolycrystalline silicon film 38 need not completely cover the drainregion (i.e., the n⁺-type semiconductor region 9) of the drive MISFETsQd₁ and Qd₂ and the drain region (i.e., the p⁺-type semiconductor region12) of the load MISFETs Qp₁ and Qp₂. In other words, there arises noproblem even if the portion (as indicated by arrow in FIG. 26) of thepolycrystalline silicon film 38 on the n⁺-type semiconductor region 9 isetched out by the mask misalignment of the photoresist 39, as shown inFIG. 26. This is because even if the polycrystalline silicon film 38 ispartially etched out, the underlying Co film 37 acts as the etchingstopper so that the polycrystalline silicon film 36 on the surfaces ofthe n⁺-type semiconductor region 9 and the p⁺-type semiconductor region12 is not etched out.

Although not especially limited, in the present embodiment, when theaforementioned polycrystalline silicon film 38 is to be etched, it isleft on such an n⁺-type semiconductor region 9 (i.e., the drain region)of the n⁺-type semiconductor region 9 (i.e., the source region and thedrain region) of the drive MISFETs Qd₁ and Qd₂ as constitutes thestorage nodes A and B of the memory cell, but not on the n⁺-typesemiconductor region 9 (i.e., the source region) which does notconstitute the storage nodes A and B. The polycrystalline silicon film38 on the n⁺-type semiconductor region 9 (i.e., the source region) neednot be wholly removed but may be partially left to cause no trouble bythe mask misalignment of the photoresist 39.

Next, this photoresist 39 is removed, and the semiconductor substrate 1is subjected to a heat treatment in the atmosphere of inert gases atabout 700° C. to cause a silicifying reaction among the polycrystallinesilicon film 38, the Co film 37 and the polycrystalline silicon film 36.Next, the unreacted Co film 37, as left on the region having nodeposition of the polycrystalline silicon films 36 and 38, is removed bythe wet etching method to form the local wiring lines L₁ and L₂ of acobalt silicide film and the cobalt silicide layers 16, 17 and 36′, asshown in FIGS. 27 and 28. FIG. 29 shows a pattern of the local wiringlines L₁ and L₂ and the cobalt silicide layers 16, 17 and 36′ for thesixteen memory cells.

Thus, in the manufacture process of the present embodiment, the pairedlocal wiring lines L₁ and L₂ connecting the storage nodes A and B of thememory cell are made of the cobalt silicide. This cobalt silicide is amaterial having a lower electric resistance than the polycrystallinesilicon and acting as an effective barrier against the diffusion of theatoms of an impurity such as P (phosphorous) or B (boron). Thanks tothis construction, therefore, the p-type impurity in the drain region(i.e., the p⁺-type semiconductor region 12) of the load MISFETs Qp₁ andQp₂ and the n-type impurity in the drain region (i.e., the n⁺-typesemiconductor region 9) of the drive MISFETs Qd₁ and Qd₂ or in the gateelectrodes 10 a and 10 b can be prevented from diffusing into each otherthrough those local wiring lines L₁ and L₂. As a result, the p⁺-typesemiconductor region 12 and the n⁺-type semiconductor region 9 of thedifferent conduction types and the gate electrodes 10 a and 10 b can beohmically connected with a low resistance to operate the memory cell ata high speed and at a low voltage.

According to the manufacture process of the present embodiment,moreover, when the local wiring lines L₁ and L₂ are to be formed, thepolycrystalline silicon film 36 is selectively formed on the individualsurfaces of the drain region (i.e., the n⁺-type semiconductor region 9)of the drive MISFETs Qd₁ and Qd₂ and the drain region (i.e., the p⁺-typesemiconductor region 12) of the load MISFETs Qp₁ and Qp₂, as constitutethe storage nodes A and B of the memory cell, and the Co film 37 and thepolycrystalline silicon film 38 are formed over the polycrystallinesilicon film 36 so that the silicifying reaction is caused among thosethree layers. Thanks to this construction, the silicons of theaforementioned n⁺-type semiconductor region 9 and p⁺-type semiconductorregion 12 constituting the storage nodes A and B of the memory cell canbe prevented from participating in the aforementioned silicifyingreaction. As a result, the cobalt silicide layers 16 and 17 can be madeshallow so that the junction leakage current of the n⁺-typesemiconductor region 9 and the p⁺-type semiconductor region 12 can bereduced to improve the operational reliability of the memory cell.

In case, on the contrary, the Co film 37 is made to directly contactwith the n⁺-type semiconductor region 9 and the p⁺-type semiconductorregion 12 without forming the polycrystalline silicon film 36, thesilicons in the n⁺-type, semiconductor region 9 and the p⁺-typesemiconductor region 12 participate in the silicifying reaction. As aresult, the cobalt silicide layers 16 and 17 are formed deep in thesubstrate (i.e., the p-type well 3 and the n-type well 4) so that thejunction leakage current to the substrate from the n⁺-type semiconductorregion 9 and the p⁺-type semiconductor region 12 increases.

Incidentally, in order that the silicons in these n⁺-type semiconductorregion 9 and p⁺-type semiconductor region 12 may not participate in thesilicifying reaction, it is sufficient to control the thickness of thepolycrystalline silicon film 36 so that this film 36 may be left,between the local wiring lines L₁ and L₂ and the underlying n⁺-typesemiconductor region 9 and p⁺-type semiconductor region 12, to have athickness larger than that of at least the gate insulating film 7 evenafter the local wiring lines L₁ and L₂ are formed by the silicifyingreaction.

Thanks to the aforementioned construction, moreover, the polycrystallinesilicon film 36 on the n⁺-type semiconductor region 9 and the p⁺-typesemiconductor region 12, as constituting the storage nodes A and B ofthe memory cell, can be prevented from being scraped off, even in thecase of a misalignment of the photoresist 39 acting as the mask foretching the overlying the polycrystalline silicon film 38. As a result,no allowance for the alignment of the photoresist 39 is required so thatthe areas of the n⁺-type semiconductor region 9 and the p⁺-typesemiconductor region 12 can be reduced to highly integrate the memorycell.

According to the manufacture process of the present embodiment,moreover, the cobalt silicide layer 16 (or 17) having a low resistanceis formed on the surfaces of at least one portion of the respectivesource regions and drain regions of the six MISFETs Qt₁ and Qt₂, driveMISFETs Qd₁ and Qd₂ and load MISFETs Qp₁ and Qp₂ constituting the memorycell. Thanks to this construction, the source regions and drain regions,as formed with the cobalt silicide layer 16 (or 17), can have theirresistances reduced to operate the memory cell at a high speed and at alow voltage.

According to the manufacture process of the present embodiment,moreover, when the aforementioned polycrystalline silicon film 38 is tobe etched, it is not left on such an N⁺-type semiconductor region 9(i.e., the source region) of the n⁺-type semiconductor region 9 (i.e.,the source region and the drain region) of the drive MISFETs Qd₁ and Qd₂as does not constitute the storage nodes A and B of the memory cell.Thanks to this construction, it is possible to prevent the disadvantage,in which the source regions and drain regions of the drive MISFETs Qd₁and Qd₂ are shorted through the polycrystalline silicon film 38 and thelocal wiring lines L₁ and L₂. As a result, it is possible to improve theproduction yield and reliability of the SRAM.

According to the manufacture process of the present embodiment,moreover, the local wiring lines L₁ and L₂ are formed in self-alignmentwith the side wall insulating film 14 of the gate electrodes (6, 10 aand 10 b). Thanks to this construction, when the local wiring lines L₁and L₂ and the n⁺-type semiconductor region 9 and the p⁺-typesemiconductor region 12 constituting the storage nodes A and B are to beconnected, no allowance is required for the mask alignment of them. As aresult, gaps Z₁ and Z₂, as taken along the extending direction of theword line WL, can be reduced, as shown in FIG. 28, to reduce the size ofthe memory cell thereby to highly integrate the memory cell.

Next, the insulating film 19 is deposited all over the surface of thesemiconductor substrate 1 by the CVD method, as shown in FIG. 30. Thisinsulating film 19 is formed by laminating a silicon nitride film havinga thickness of about 10 nm on a silicon oxide film having a thickness ofabout 10 nm.

Next, as shown in FIG. 31, the aforementioned insulating film 19 isremoved from the drain region (i.e., the n⁺-type semiconductor region 9)of the transfer MISFETs Qt₁ and Qt₂ to form the connection hole 23 bythe dry etching method using a photoresist PL6 as the mask. Moreover,the insulating film 19 is removed from the source region (i.e., thep⁺-type semiconductor region 12) of the load MISFETs Qp₁ and Qp₂ andfrom the n⁺-type semiconductor region 18 adjacent to that wellenergizing source region, thereby to form the connection hole 25.Although not shown, moreover, the insulating film 19 is removed from thesource region (i.e., the n⁺-type semiconductor region 9) of the driveMISFETs Qd₁ and Qd₂ to form the connection hole 21.

Next, the polycrystalline silicon film having a thickness of about 70 nmis deposited all over the surface of the semiconductor substrate 1 bythe CVD method. Then, this polycrystalline silicon film is patterned bythe dry etching method using a photoresist as the mask to form thereference voltage line 20, the pad layer 22 and the pad layer 24, asshown in FIGS. 32 and 33. The reference voltage line 20 is arranged tocover the local wiring lines L₁ and L₂ and is connected through theconnection hole 21 with the source region (i.e., the n⁺-typesemiconductor region 9) of the drive MISFETs Qd₁ and Qd₂; The pad layer22 is connected through the connection hole 23 with the cobalt silicidelayer 16, and the pad layer 24 is connected through the connection hole25 with the cobalt silicide layer 17. FIG. 34 shows the referencevoltage line 20 and the pad layers 22 and 24 for the sixteen memorycells.

Next, as shown in FIG. 35, the inter-layer insulating film 26 isdeposited all over the surface of the semiconductor substrate 1 by theCVD method. This inter-layer insulating film 26 is formed by laminatinga BPSG film 26 b having a thickness of about 300 nm on a silicon oxidefilm 26 a having a thickness of about 150 nm and subsequently byflattening the BPSG film by the reflow.

Next, the inter-layer insulating film 26 is formed with the connectionholes 31 and 33 by the dry etching method using the photoresist as themask. Then, the Al alloy film is deposited to a thickness of about 300nm all over the surface of the semiconductor substrate 1 by thesputtering method to form the supply voltage line 27, the sub-referencevoltage line 28, the sub-word line 29 and the pad layer 30 over theinter-layer insulating film 26, as shown in FIGS. 36 and 37.

Thus, according to the manufacture process of the present embodiment,when the supply voltage line 27 is to be connected with the sourceregions (i.e., the p⁺-type semiconductor region 12) of the load MISFETsQp₁ and Qp₂ and the n⁺-type semiconductor region 18 adjacent to the wellenergizing source region through the connection hole 31 opened in theinter-layer insulating film 26, the polycrystalline silicon pad layer 24is formed in advance on the p⁺-type semiconductor region 12 and then⁺-type semiconductor region 18. Moreover, when the pad layer 30 isconnected with the drain region (i.e., the n⁺-type semiconductor region6) of the transfer MISFETs Qt₁ and Qt₂ through the connection hole 33opened in the inter-layer insulating film 26, the polycrystallinesilicon pad layer 22 is formed in advance on the n⁺-type semiconductorregion 6.

Thanks to this construction, when the inter-layer insulating film 26 isetched to form the connection holes 31 and 33, none of the cobaltsilicide layers 16 and 17 are exposed to the bottom portion of theconnection holes 31 and 33 so that the cobalt silicide layers 16 and 17can be prevented from being scraped.

According to the manufacture process of the present invention, moreover,when the source region (i.e., p⁺-type semiconductor region 12) of theload MISFETs Qp₁ and Qp₂ and the well energizing n⁺-type semiconductorregion 18 adjacent to that source region are to be connected with thesupply voltage line 27, they are formed in advance on their surfaceswith the cobalt silicide layer 16. Thanks to this construction, thep⁺-type semiconductor region 12 and the n⁺-type semiconductor region 18can be ohmically connected with the supply voltage line 27 withoutconsidering the conduction type of the polycrystalline silicon pad layer24 formed on the cobalt silicide layer 16, so that they can besimultaneously supplied with the supply voltage (V_(cc)) through thesingle connection hole 31. As a result, the p⁺-type semiconductor region12 and the n⁺-type semiconductor region 18 can be arranged adjacent toeach other to have their areas reduced to highly integrate the memorycell.

Next, the inter-layer insulating film 34 is deposited all over thesurface of the semiconductor substrate 1, as shown in FIG. 38. Thisinter-layer insulating film 34 is formed by spin-applying the spin-onglass (SOG) film 34 b having a thickness of about 250 nm to the siliconoxide film 34 a deposited to have a thickness of about 500 nm by the CVDmethod, subsequently by etching back to flatten the surface of thespin-on glass film 34 b and by depositing the silicon oxide film 34 chaving a thickness of about 400 nm thereon by the CVD method.

After this, the inter-layer insulating film 34 is formed with theconnection hole 35 by the dry etching using the photoresist as the mask.After this, the Al alloy film is deposited all over the surface of thesemiconductor substrate 1 by the sputtering method, and is thenpatterned to form the data line DL and the barred data line DL by thedry etching method using the photoresist as the mask, thus completingthe memory cell of the SRAM of the present embodiment. FIG. 39 shows thedata lines DL and the barred data lines DL for the sixteen memory cells.

Although our invention has been specifically described in connectionwith its embodiment, it should not be limited thereto but can naturallybe modified in various manners without departing from the gist thereof.

When the local wiring lines L₁ and L₂ are to be formed, the drain region(i.e., the n⁺-type semiconductor region 9) of the drive MISFETs Qd₁ andQd₂ and the drain region (i.e., the p⁺-type semiconductor region 12) ofthe load MISFETs Qp₁ and Qp₂, as constitute the storage nodes A and B ofthe memory cell, are formed on their individual surfaces with thepolycrystalline silicon film 36, the Co film 37 and the polycrystallinesilicon film 38 so that the silicifying reaction is caused among thosethree layers. However, the underlying polycrystalline silicon film 36 isnot always necessary, but the silicifying reaction can be caused betweenthe Co film 37 and the polycrystalline silicon film 38 deposited on theformer, to form the local wiring lines L₁ and L₂.

In this case, the step of selectively depositing the polycrystallinesilicon film 36 on the surface of the aforementioned drain regions(i.e., the n⁺-type semiconductor region 9 and the p⁻-type semiconductorregion 12) can be eliminated to reduce the number of steps ofmanufacturing the memory cell. In this case, however, the Co film 37 isdirectly deposited on the surface of the drain region (i.e., the n⁺-typesemiconductor region 9 and the p⁻-type semiconductor region 12). Inorder to prevent the silicifying reaction from progressing between thesilicon of the drain region and the Co film 37, therefore, the overlyingpolycrystalline silicon film 38 has to be made so sufficiently thick asto feed the silicon necessary for the silicifying reaction to thepolycrystalline silicon film 38.

If, moreover, the polycrystalline silicon film 38 on the aforementioneddrain region (i.e., n⁺-type semiconductor region 9 and the p⁺-typesemiconductor region 12) is partially etched when the overlyingpolycrystalline silicon film 38 is to be patterned by the dry etchingmethod using the photoresist as the mask, the silicifying reactionbetween the drain region and the Co film 37 progresses. Therefore, asufficient allowance for the mask alignment has to be retained so thatthe polycrystalline silicon film 38 may be sufficiently superposed overthe drain region (i.e., the n⁺-type semiconductor region 9 and thep⁺-type semiconductor region 12) and prevented from being scraped.

Moreover, when the local wiring lines L₁ and L₂ are to be formed by thesilicifying reaction, the deposition thickness of the aforementionedpolycrystalline silicon film 38 to be deposited on the Co film 37 may bemade thicker than that necessary for the silicifying thereby to leavethe unreacted polycrystalline silicon film on the cobalt silicide layer.Alternatively, a refractory metal film or a refractory metal silicidefilm may be further deposited on the polycrystalline silicon film 38.Then, as shown in FIG. 40, the thickness of the local wiring lines L₁and L₂ is larger than that of the case of the single cobalt silicidelayer so that the local wiring lines L₁ and L₂ can have a larger surfacearea. As a result, a capacity (C₂) to be established between the localwiring lines L₁ and L₂ and the overlying reference voltage line 20 canbe increased to increase the storage node capacity of the memory cellthereby to improve the resistance to the α ray soft error.

In this case, as shown in FIG. 40, the unreacted polycrystalline siliconfilm is left not only on the cobalt silicide layer 16 formed on thesurface of the drain region (i.e., the n⁺-type semiconductor region 9)of the transfer MISFETs Qt₁ and Qt₂ but also the cobalt silicide layer17 formed on the surface of the source region (i.e., p-typesemiconductor region 12) of the load MISFETs Qp₁ and Qp₂. As a result,the pad layers 22 and 24 need not be formed of the polycrystallinesilicon film belonging to the same layer as that of the referencevoltage 20 on the cobalt silicide layers 16 and 17, so that the area ofthe memory cell can be reduced. When the pad layers 22 and 24 belongingto the same layer as that of the reference voltage line 20 areunnecessary, the area to be occupied by the reference voltage line 20can be enlarged, as shown in FIG. 41, to further increase the storagenode capacity of the memory cell thereby to improve the resistance tothe a ray soft error.

In the embodiment thus far described, a capacity (C) is formed betweenthe local wiring lines L₁ and L₂ and the overlying reference voltageline 20. As shown in FIG. 41, however, the power supplying pad layer 24,as formed of the same polycrystalline silicon film as that of thereference voltage line 20, has its area enlarged to cover the localwiring lines L₁ and L₂ thereby to form a capacity between that pad layer24 and the local wiring lines L₁ and L₂. In this case, the referencevoltage line 20 is left only over the source region (i.e., the n⁺-typesemiconductor region 9) of the drive MISFETs Qd₁ and Qd₂.

In the memory cell of the SRAM of the foregoing embodiment, the gateelectrode 6 (of the word line WL) of the transfer MISFETs Qt₁ and Qt₂ isformed of the polycrystalline silicon film belonging to the same layeras the gate electrodes 10 a and 10 b of the drive MISFETs Qd₁ and Qd₂and the load MISFETs Qp₁ and Qp₂ but may also be formed of thepolycrystalline silicon film (e.g., the polycrystalline silicon filmbelonging to the same layer as the reference voltage line 20) overlyingthe gate electrodes 10 a and 10 b. In this case, as shown in FIG. 43,the gate electrode 6 (i.e., the word line WL) and the gate electrodes 10a and 10 b can be arranged to have their portions partially superposed,so that the area of the memory cell can be reduced to highly integratethe SRAM. Moreover, the present invention has been described inconnection with the CMOS inverters (INV₁, INV₂), but the descriptionshould not be limited thereto but can naturally be exemplified by a CMIS(i.e., Complementary-MIS). This exemplification applies to the followingEmbodiments 2 to 17.

The effects to be obtained by the representative of the inventiondisclosed by the present embodiment will be briefly described in thefollowing.

The reference voltage line 20 to be formed over the local wiring linesL₁ and L₂ is arranged to be superposed over the local wiring lines L₁and L₂ so that the capacity element C₂ is formed between the referencevoltage line 20 and the local wiring lines L₁ and L₂. As a result, thecapacity of the storage nodes A and B, as connected with the localwiring lines L₁ and L₂, can be increased to improve the resistance ofthe memory cell to the α ray soft error.

The local wiring lines L₁ and L₂ are arranged to be partially superposedover the gate electrodes 10 a, 10 b and 6(WL) of the drive MISFETs, theload MISFETs or the transfer MISFETs so that the capacity element C₁ canbe formed between the local wiring lines and the gate electrodes toincrease the gate capacity component C₁ of the storage node capacity. Asa result, the storage node capacity of the memory cell can be increasedto improve the resistance to the α ray soft error.

The local wiring lines L₁ and L₂ are arranged to be partially superposedover the storage nodes A and B of the memory cell so that the capacitycomponent of the diffusion layer of the storage node capacity can beincreased. As a result, the storage node capacity of the memory cell canbe increased to improve the resistance to the α ray soft error.

Over the reference voltage line 20, there is arranged the wiring line 28having a lower resistance, and the electric power is supplied from thelower-resistance wiring line 28 to the reference voltage 20 through theconnection holes which are formed in at least one in each memory cell.As a result, the electric power of the reference voltage line 20 can besupplied to each memory cell so that the reference voltage can bestabilized. As a result, the minimum value (V_(cc.min)) of the supplyvoltage can be improved to improve the resistance of the memory cell tothe a ray soft error.

The connection holes 32 for connecting the lower-resistance wiring line28 and the reference voltage line 20 and the connection holes 21 forconnecting the reference voltage line 20 and the source region 9 of thedrive MISFETs are spaced from each other so that the step, which mightotherwise be formed by the overlap of those connection holes, can beavoided to flatten the connection hole forming regions. As a result, theconnection holes can have their contact resistances reduced to operatethe memory cell at a high speed and at a low voltage.

The local wiring lines L₁ and L₂ are formed by causing the silicifyingreaction among the polycrystalline silicon film 36, the refractory metalfilm 37 deposited on the former, and the second polycrystalline siliconfilm 38 deposited on the former, so that the silicon in thesemiconductor regions forming the storage nodes A and B of the memorycell can be prevented from participating in the aforementionedsilicifying reaction. As a result, the junction leakage current of thesemiconductor regions 9 and 12 can be reduced to improve the operationalreliability of the memory cell.

The step of forming the connection holes 15 in the portions of the gateelectrodes 10 a and 10 b and the step of exposing the semiconductorregions 9, 12 and 18 are carried out separately of each other to makethe allowance unnecessary for the mask alignment between the connectionholes 15 and the semiconductor regions 9, 12 and 18, so that the areasfor the connection holes can be reduced to highly integrate the memorycell. By connecting the local wiring lines L₁ and L₂ and thesemiconductor regions 9, 12 and 18 in self-alignment, moreover, noallowance is required for the mask alignment of the two so that thememory cell size can be reduced to highly integrate the memory cell.

The paired local wiring lines L₁ and L₂ for connecting the storage nodesA and B of the memory cell are made of the refractory metal silicide, sothat the p-type impurity in the semiconductor region 12 of the loadMISFETs and the n-type impurity in the semiconductor region 9 or thegate electrodes 10 a and 10 b of the drive MISFETs can be prevented fromdiffusing into each other through the local wiring lines L₁ and L₂. As aresult, the ohmic connections can be made with a low resistance betweenthe semiconductor regions 12 and 9 of the different conduction types andbetween the semiconductor region 12 and the gate electrodes 10 a and 10b thereby to operate the memory cell at a high speed and at a lowvoltage.

Even in the case of a misalignment of the photoresist 39 to be used asthe mask at the time of etching the overlying polycrystalline siliconfilm 38, it is possible to prevent the underlying polycrystallinesilicon film 36 from being scraped. As a result, the allowance for thealignment of the photoresist 39 can be eliminated to reduce the areasfor the semiconductor regions 9 and 12 thereby to highly integrate thememory cell.

The refractory metal silicide layers 16 and 17 are formed on thesurfaces of at least the portions of the individual source regions anddrain regions of the transfer MISFETs Qt₁ and Qt₂, the drive MISFETs Qd₁and Qd₂ and the load MISFETs Qp₁ and Qp₂, as constituting the memorycell, so that the source regions and the drain regions can have theirresistances lowered. As a result, it is possible to operate the memorycell at a high speed and at a low voltage.

The source region 12, the well energizing drain region 18 and the supplyvoltage line 27 can be ohmically connected without considering theconduction type of the polycrystalline silicon pad layer 24, as formedon the refractory metal silicide layer 16, so that the source region 12and the well energizing drain region 18 of the load MISFETs can besimultaneously supplied with the supply voltage (V_(cc)) through the oneconnection hole 31. As a result, the source region 12 and the wellenergizing drain region 18 of the load MISFETs can be arranged adjacentto each other and can have their areas reduced to highly integrate thememory cell.

When the local wiring lines L₁ and L₂ are to be formed by thesilicifying reaction, their thickness and surface areas are increased bymaking the polycrystalline silicon film 38, as deposited on therefractory metal silicide layer 37, thicker than that necessary for thatsilicifying reaction, so that the capacity to be established between thelocal wiring lines L₁ and L₂ and the overlying reference voltage line 20is increased. As a result, the storage node capacity of the memory cellcan be further increased to improve the resistance to the a ray softerror.

Embodiment 2

The present embodiment is a second one of the present invention, whichis different from the foregoing Embodiment 1 in the process of formingthe local wiring lines L₁ and L₂. FIGS. 44 and 45 are top plan viewsshowing a portion of 1 bit in the present embodiment, and FIG. 46 showsa sectional structure taken in the direction of line Y-Y of FIG. 44.Specifically, FIG. 44 is a top plan view showing the n-channel drive MIStransistors and transfer MIS transistors and the p-channel load MIStransistors, and FIG. 45 is a top plan view showing the two-layeredelectrode wiring lines. The equivalent circuit diagram of the memorycell is identical to that shown in FIG. 3 excepting the capacity elementC₂. The paired drive MIS transistors Qd₁ and Qd₂, the paired transferMIS transistors Qt₁ and Qt₂ and the paired load MIS transistors Qp₁ andQp₂, which have their one gate crossly connected with the drain of theother, are individually connected with the storage nodes A and B.

In FIG. 44, the drain of the drive MIS transistor Qd₁ and the source ordrain of the transfer MIS transistor Qt₁ are made of a common heavilydoped n-type impurity region 102, and the drain of the drive MIStransistor Qd₂ and the drain (or source) of the transfer MIS transistorQt₂ are made of a common heavily doped n-type impurity region 105.Moreover, the common gate electrode 113 of the drive MIS transistor Qd₁and the load MIS transistor Qp₁ is connected through an opening 116 witha local wiring line 120 (i.e., L₂), through an opening 115 with theheavily doped n-type impurity region 105 and further through an opening117 with a heavily doped p-type impurity region 110 forming the drain ofthe load MIS transistor Qp₂. Likewise, the common electrode 114 of thedrive MIS transistor Qd₂ and the load MIS transistor Qp₂ is connectedthrough the opening 116 with a local wiring line 119 (i.e., L₁), throughthe opening 115 with the heavily doped n-type impurity region 102, andfurther through the opening 117 with a heavily doped p-type impurityregion 108 forming the drain of the load MIS transistor Qp₁. Thus, thereare individually formed the storage nodes A and B, which are indicatedin the equivalent circuit of the static type random access memory cellof FIG. 43.

On the other hand, a common gate electrode 111 of the transfer MIStransistors Qt₁ and Qt₂ forms a word line 155 in FIG. 43. Incidentally,a gate electrode 112 belongs to a transfer MIS transistor of an adjacentcell.

Moreover, with openings 123 and 124 of the source or drain of thetransfer MIS transistors Qt₁ and Qt₂, as made of heavily doped n-typeimpurity regions 103 and 106, there are individually connectedfirst-layered aluminum electrodes 127 and 128, as shown in FIG. 45, anddata lines made of overlying second-layered aluminum electrodes 133 and134 through openings 131 and 132. With the source regions of the driveMIS transistors Qd₁ and Qd₂ made of heavily doped n-type impurityregions 101 and 104 of FIG. 41, moreover, there are connected throughopenings 121 and 122 the ground wiring lines which are made of a commonfirst-layered aluminum electrode 129, as shown in FIG. 45.

With the source regions of the load MIS transistors Qp₁ and Qp₂ made ofheavily doped p-type impurity regions 107 and 109 of FIG. 44, on theother hand, there are individually connected through openings 125 and126 the supply wiring lines made of a common first-layered aluminumelectrode 130, as shown in FIG. 45, to supply a predetermined potentialto all the memory cells.

Next, the structure of the local wiring lines will be described withreference to the section of FIG. 46. FIG. 46 is a section of the SRAMcell, as taken along line Y-Y′ of FIG. 44. In FIG. 46, an n-type siliconsubstrate 135 is formed with a p-well 136 and an n-well 137 respectivelyhaving a depth of 2 μm, a field oxide film 138 having a thickness of 400nm, and a gate oxide film 139 having a thickness of 10 nm. All the gateelectrodes 111 and 112 of the transfer MIS transistors, the gateelectrode 113 of the drive MIS transistors and the gate electrode 114 ofthe load MIS transistors are made of a polycrystalline silicon filmhaving a thickness of 200 nm. Moreover: the heavily doped n-typeimpurity region 102 is the common drain (or source) of the drive MIStransistors and the transfer MIS transistors; the heavily doped n-typeimpurity region 103 is the common drain (or source) of the transfer MIStransistors; and the heavily doped p-type impurity region 110 is thedrain of the load MIS transistors.

The surfaces of the gate electrodes 111 and 112 of the transfer MIStransistors, a portion of the gate electrode 114 of the drive MIStransistors, and the entire or partial surfaces of the heavily dopedn-type impurity regions 102 and 103 and the heavily doped p-typeimpurity region 110 are formed by the silicifying technique with atitanium silicide film 142 having a thickness of 50 nm to reduce theirresistances. Moreover, the titanium silicide films 142 over the heavilydoped n-type impurity region 102 and the heavily doped p-type impurityregion 110 are automatically connected with each other through thetitanium silicide film 142 which is also formed over a silicon oxidefilm 141. Moreover, a silicon oxide film 143, as lying over the titaniumsilicide film 142 over the heavily doped n-type impurity region 103, isformed with contact holes and connected with the first-layered aluminumelectrode 127.

Next, the steps of manufacturing the present embodiment will bedescribed with reference to FIGS. 47( a) to 47(c), FIGS. 48( a) to 48(c)and FIGS. 49( a) to 49(b). FIGS. 47( a) to 49(b) are sections takenalong line Y-Y′ from the top plan view of FIG. 44.

First of all, as shown in FIG. 47( a), the n-type silicon substrate 135having a specific resistance of about 10Ωcm is formed in a dosage ofabout 1×10¹⁶ atoms/cm² with the p-type well 136 and the n-type well 137having a depth of 1 μm by the ion implantation and the thermal diffusionmethod and then with the element isolating silicon oxide film (i.e., thefield oxide film 138) having a thickness of 400 nm by the well-knownselective oxidation method. Subsequently, the portion for the activeregion of the MIS transistors is formed with the gate oxide film 142having a thickness of about 10 nm. Here, when the field oxide film 138is formed, a n-inversion preventing channel stopper layer is ordinarilyformed below the field oxide film in the p-type well 136 but is notshown in the Figure. Incidentally, the channel stopper layer may beformed by the ion implantation method after the field oxide film isformed. On the other hand, the wells may have an impurity concentrationdistribution made to have the higher concentration in the depthwisedirection. In this case, the ion implantation for forming the p-typewell can be carried out after the field oxide film is formed. In thiscase, moreover, the ion implantation may be carried out with a pluralityof kinds of energy. Then, the ion implantation is carried out foradjusting the threshold voltage of the MOS transistors. For this properion implantation, for example, BF₂ ions are implanted in a dosage ofabout 2×10¹² atoms/cm² by the energy of 40 KeV. Incidentally, the ionimplantation for adjusting the threshold voltage can prevent the gateoxide film from being damaged or contaminated at the ion implantingstep, if it is carried out before the gate oxidizing step.

Next, as shown in FIG. 47( b), for example, a polycrystalline siliconfilm having a thickness of 200 nm is deposited by the low pressurechemical vapor deposition (i.e., LPCVD) so that it is doped with animpurity to have its resistance lowered. The doping method of theimpurity is carried out by introducing an n-type impurity such asphosphor by the vapor phase diffusion. Subsequently, the polycrystallinesilicon film is patterned into the gate electrodes 111 to 114 by thephotolithography and the dry etching method. Subsequently, by usingthese gate electrodes and photoresists as the masks for the ionimplantations, the n-channel MIS transistors are doped with the ions ofan n-type impurity such as arsenic in a dosage of about 2×10¹⁵atoms/cm², and the p-channel regions are doped with the ions of a p-typeimpurity such as boron in a dosage of about 2×10¹⁵ atoms/cm². Theimpurity ions are annealed in the nitrogen atmosphere at 850° C. so thatthey are activated to form the heavily doped n-type impurity regions 102and 103 and the heavily doped p-type impurity region 110 having a depthof about 0.1 μm. Incidentally, in order to prevent the reduction of thelong-term reliability of the MOS transistors, there may be adopted theso-called “LDD (i.e., Lightly Doped Drain) structure”, in which the MOStransistors have their source/drain formed with a lightly doped n-typeimpurity region, although not described in the present embodiment.Moreover, the method of doping the polycrystalline silicon film of thegate electrode with the impurity may also be exemplified by the ionimplantation at the source/drain forming time or by the (dopedpoly-silicon) method at the time of forming the polycrystalline siliconfilm.

Next, as shown in FIG. 47( c), the silicon oxide film having a thicknessof about 150 nm is deposited by the LPCVD method of thermallydecomposing monosilane gas and is then etched back by the anisotropicdry etching method to form a spacer insulating film 140 on the sidewalls of the gate electrodes 111 to 114 thereby to expose the heavilydoped impurity regions of the upper portion of the gate electrode andthe silicon substrate surface to the outside. Next, the silicon oxidefilm 141 having a thickness of about 30 nm is deposited by a similarLPCVD method, and an amorphous silicon film 145 having a thickness ofabout 50 nm is subsequently deposited on the silicon oxide film 141 at atemperature of about 520° C. by the LPCVD method. Next, the amorphoussilicon film 145 is patterned into the shape of the local wiring linesL₁ and L₂ by the photolithography and the dry etching method.Incidentally, the amorphous silicon film 145 may be replaced by apolycrystalline silicon film (as shown in FIG. 48( a)).

Next, as shown in FIG. 48( b), a photoresist 146 is used as the mask toform the openings (115 to 118 of FIG. 44) in the aforementioned siliconoxide film 141 by the dry etching method. Here, the amorphous siliconfilm 145 is partially exposed to the openings, but the silicon oxidefilm 141 of this portion is not dry-etched.

Next, as shown in FIG. 48( c), a titanium film 147 having a thickness of50 nm is deposited all over the surface by the sputtering method.

Next, as shown in FIG. 49( a), a heat treatment is carried out in thenitrogen atmosphere to form the titanium silicide film 142 on theexposed heavily doped n-type impurity regions 102 and 103 and heavilydoped p-type impurity region 110, the exposed gate electrodes 111, 112and 114 and the exposed amorphous silicon film 145. The titanium leftunreacted is removed by an aqueous solution of hydrogen peroxide or thelike. Incidentally, at the time of forming the titanium silicide, theconditions for the thermal treatment are such that the titanium silicidefilm 142 on the silicon substrate is caused by the heat treatment tocreep up the step of the silicon oxide film 141 into contact with thetitanium silicide film 142 which is formed by the reaction with theamorphous silicon film 145. At this time, the titanium silicide film 142an the gate-electrode 113 are insulated by the silicon oxide film 141.Next, the resistance of the titanium silicide film 142 is lowered by anannealing treatment in the nitrogen atmosphere at a temperature of 800°C.

Next, as shown in FIG. 49( b), the silicon oxide film 143 is depositedon the aforementioned titanium silicide film 142 and is formed with theopenings 121 to 126 (although not shown in FIG. 49), as shown in FIG.44, by the photolithography and the dry etching method. Subsequently,the first-layered aluminum electrodes 127, 129 and 130 are patterned bythe photolithography and the dry etching method. Incidentally, thetemperature for forming the silicon oxide film is desired to be so lowthat the composition of the titanium silicide film may not beinfluenced.

Incidentally, the present embodiment has been described in connectionwith only the memory cell. However, the source/drain of the CMIStransistor group and the gate electrodes around the memory cell can alsobe silicified by etching the silicon oxide film 141 of a desired portionas in the word lines of the memory cell. Moreover, the presentembodiment has been described in connection with the titanium silicidebut can use another material such as a cobalt silicide, which is liableto creep up on the oxide film. In addition, there can be used a chemicalcompound (I.e., a refractory metal silicide) of a known refractory metaland silicon, such as platinum silicide (PtSi_(x)), nickel silicide(NiSi_(x)), tungsten silicide (WSi_(x)) or tantalum silicide (TaSi_(x)).

Moreover, a refractory metal such as cable of selectively growing on thesilicon surface is enabled to grow directly on the silicon substrate,the gate electrodes or the amorphous silicon film. In this case, thegrowing condition for tungsten may be exemplified by the CVD methodusing tungsten hexafluoride gas.

According to the present embodiment, it is simultaneously possible tosilicify the titanium on the silicon substrate and the gate electrodesand to form the local wiring lines of the laminated structure. As aresult, the source/drain and the gate electrodes can have theirresistances lowered without any drastic increase in the step number, andthe memory cell area can also be reduced by using the local wiring linesof the laminated structure in the intersections of the memory cells.According to the present embodiment, moreover, the drive MIS transistorsare formed on their drain ends with the local wiring lines which areconnected with the heavily doped h-type impurity regions of the drain sothat they are at the same potential as that of the drains. In case,therefore, the LDD structure is adopted in the MIS transistors, thereduction of the driving ability by the LDD layer can be suppressed bythe fringe electric field of the local wiring lines, to provide a memorycell having a stable operation and excellent noise characteristics.Incidentally, the logic elements other than the memory cell are formedof three or more aluminum wiring lines, although not shown. In thepresent embodiment, the logical elements of the microprocessor areformed on the silicon substrate 135 and are composed of the MISFETshaving the same construction as that of the transfer MISFETs Qt₁ andQt₂. In short, the logic elements are formed of the MISFETs having theirgate electrode formed of the polycrystalline silicon electrodes 111 andthe titanium silicide film 142.

Embodiment 3

The present embodiment relates to a method of connecting the localwiring lines and the silicon substrate. FIG. 50 presents a sectionalstructure of a SRAM memory cell according to the present embodiment andshows the portion of the local wiring lines of the section along lineA-A′ of FIG. 48( b), in an enlarged scale. The steps when and before theMIS transistors are formed on the silicon substrate are identical tothose at and before FIG. 48( b) of Embodiment 2. In FIG. 50, the heavilydoped n-type impurity region 102 exposed to the openings of the siliconoxide film 141 and the gate electrodes 114 of the drive MIS transistorsare selectively grown with the polycrystalline silicon and connected inself-alignment with the amorphous silicon film 145 which is patternedinto the pattern of the local wiring lines. The means for selectivelygrowing the polycrystalline silicon is the LPCVD method usingdichlorosilane and hydrogen chloride gas at a temperature of 750° c. to800° C. Incidentally, in this case, too, the polycrystalline siliconfilm selectively grows on the source/drain and the gate electrodes ofthe CMIS transistors of the peripheral circuit other than the memorycell group. If, however, the growth distance of the polycrystallinesilicon film is controlled to the step of the silicon oxide film, thesource/drain and gate electrodes will not be shorted. Incidentally,according to the aforementioned manufacture process, the polycrystallinesilicon film is grown on the amorphous silicon film 145 but is notshown. The subsequent steps may be absolutely identical to those ofEmbodiment 2 on and after FIG. 48( c).

According to the present embodiment, the silicon substrate and the gateelectrodes and the local wiring lines can be easily connected. In theperipheral CMIS transistors, moreover, the polycrystalline silicon alsogrows on the source/drain and acts as a source for supplying silicon atthe time of forming the silicide so that the silicon in the heavilydoped impurity region is not consumed by the silicifying reaction. As aresult, the leakage current at the pn junction portion can be reduced.

Embodiment 4

The present embodiment relates to a method for connecting the localwiring lines and the silicon substrate, but is different from that ofEmbodiment 3. FIG. 51 presents a sectional structure of the SRAM memorycell according to the present embodiment and shows only the portion ofthe local wiring lines of the section of FIG. 44, in an enlarged scale.The steps when and before the MIS transistors are formed on the siliconsubstrate are identical to those at and before FIG. 48( b) of Embodiment2. In FIG. 48( b), the silicon oxide film 141 is exposed through theopenings to the outside, and the amorphous silicon of 50 nm is depositedall over the surface. Next, side walls 149 of amorphous silicon areformed on the heavily doped n-type impurity region 102 and on the sidewalls of the silicon oxide film 141 in the openings of the gateelectrodes 114 of the drive MIS transistors and the amorphous siliconfilm 145, as shown in FIG. 51, by the dry etching back method, and theamorphous silicon film 145 of the local wiring pattern, the heavilydoped n-type impurity region 102 and the gate electrodes 114 areconnected. Incidentally, in this case, the source/drain and gateelectrodes of the MIS transistors are etched back, but this etching rateis desired to be properly controlled to raise no problem. The subsequentsteps may be absolutely identical to those at and after FIG. 48( c) ofEmbodiment 2.

According to the present embodiment, the silicon substrate and the gateelectrodes and the local wiring lines can be easily connected.

Embodiment 5

The present embodiment relates to a method for connecting the localwiring lines and the silicon substrate, which is different from those ofEmbodiments 3 and 4. FIG. 52 presents a sectional structure of the SRAMmemory cell according to the present embodiment and shows only theportion of the local wiring lines of the section of FIG. 44, in anenlarged scale. The steps till the MIS transistors are formed on thesilicon substrate are identical to those at and before FIG. 48( b) ofEmbodiment 2. After the openings are formed in the silicon oxide film141, as shown in FIG. 48( b), the photoresist 146 used at the openingforming time is left as it is, and the silicon oxide film 141 underlyingthe amorphous silicon film 145 exposed to the openings of the siliconoxide film 141, as shown in FIG. 51, is side-etched. This side etchingmethod is properly exemplified by the wet etching method using anaqueous solution of hydrofluoric acid. The subsequent steps may beabsolutely identical to those at and after FIG. 48( c) of Embodiment 2.

According to the present embodiment, the silicon substrate and the gateelectrodes and the local wiring lines can be easily connected.

Embodiment 6

The present embodiment relates to the capacity element C₁ using the gateelectrodes and the local wiring lines in the SRAM cell of Embodiment 2.FIG. 53 is a section of the SRAM memory cell according to the presentembodiment. In FIG. 53, a silicon nitride film 150 having a thickness of20 nm is deposited by the LPCVD method on the gate electrodes of thedrive MIS transistors and is overlaid by the titanium silicide film 142of the local wiring lines. As a result, the gate electrodes 113, thenitride film 150 and the titanium silicide film 142 constitute thecapacity element C₁ to be connected between the storage nodes.

In the present embodiment, the capacity element C₁ has its insulatingfilm 150 formed of a silicon nitride film, which may be replaced by acomposite film of a silicon nitride film and a silicon oxide film. Thismaterial may also be exemplified by an insulating film material having adielectric constant such as tantalum pentoxide.

Next, the memory cell will be described with reference to the top planview of FIG. 54. As shown in FIG. 54, the electrodes have their areasenlarged to increase the capacity of the capacity element C₁ of theaforementioned storage nodes. In FIG. 54, the heavily doped n-typeimpurity region 102 of the storage node is connected with a titaniumsilicide 153 of the local wiring lines, to form the capacity element C₁between itself and an underlying gate electrode 151 which is connectedwith the opposite storage node. On the other hand, the heavily dopedn-type impurity region 105 of the opposite storage node is connectedwith a titanium silicide film 154 of the local wiring lines to form thecapacity element C₁ between itself and an underlying gate electrode 152which is connected with the storage node. Thus, between the storagenodes A and B of the SRAM, there can be connected in parallel the twocapacity elements which are formed of the gate electrodes of the driveMIS transistors and the laminated titanium silicide film, as indicatedat C₁ in FIG. 55.

According to the present embodiment, the capacity element C₁ can beformed between the storage nodes of the SRAM with neither increasing thenumber of manufacture steps nor enlarging the memory cell areas. As aresult, the storage capacity of the storage nodes can be efficientlyincreased to prevent the malfunction of the memory cell, which mightotherwise be caused when the memory cell is irradiated with the α ray.

Embodiment 7

The present embodiment relates to a method of forming contact holes inthe SRAM cell of Embodiment 2. FIG. 56 is a top plan view showing theSRAM memory cell according to the present embodiment. As shown in FIG.56, the heavily doped n-type impurity regions 101 and 104 of the sourceregions of the drive MIS transistors are formed with openings 158 and159 and the titanium silicide film which has been described inconnection with Embodiment 2. Likewise, the heavily doped p-typeimpurity regions 107 and 109 of the source regions of the load MIStransistors are formed with openings 160 and 161 and the titaniumsilicide film 142 which has been described with reference to FIG. 46 ofEmbodiment 2. Incidentally, the present embodiment has a structuresimilar to Embodiment 2, as shown in FIG. 44, excepting the structure ofthe portion other than the openings 158 to 161, as shown in FIG. 56.Hence, the description of the remaining structure will be omitted.

In case, on the other hand, the present embodiment is applied toEmbodiment 6, the silicon nitride film 150 to be used as the insulatingfilm for the capacity element C₁, as shown in FIG. 53, is etched off bythe dry etching step of the aforementioned openings 158 to 161. As aresult, the silicon nitride film 150 is not left on those portions ofthe heavily doped n-type impurity regions 101 and 104 and the heavilydoped p-type impurity regions 107 and 109, which are to be formed withthe contact holes.

According to the present embodiment, all the openings 121 to 126, asformed for connecting the first-layered aluminum electrodes with theheavily doped impurity regions on the silicon substrate, are formed withthe titanium silicide at the silicifying step so that the cleaningtreatment to be executed for depositing the first-layered aluminumelectrodes can be facilitated. This cleaning treatment is exemplified bythe sputter cleaning method using argon gas, for example. Moreover, theportions to be formed with the contact holes are cleared of the siliconnitride film for forming the capacity element C₁ so that the aluminumwiring lines can be prevented from being broken in the contact holes.

Embodiment 8

The present embodiment relates to a local wiring line having a poly-cidestructure. FIG. 57 present a section of the SRAM cell of Embodiment 2,as taken along line Y-Y′ of FIG. 44. In FIG. 57, the n-type siliconsubstrate 135 is formed with the p-well 136 and the n-well 137 having adepth of 2 μm, the field oxide film 138 having a thickness of 400 nm,and the gate oxide film 139 having a thickness of 10 nm. The gateelectrodes 111 and 112 of the transfer MOS transistors, the gateelectrode 113 of the drive MOS transistors and the gate electrodes 114of the load MOS transistor are all formed of a polycrystalline siliconfilm having a thickness of 200 nm. Moreover: the heavily doped n-typeimpurity region 102 forms the common drain (or source) of the drive MOStransistors and the transfer MOS transistors; the heavily doped n-typeimpurity region 103 forms the common drain (or source) of the transferMOS transistors; and heavily doped p-type impurity region 110 forms thedrains of the load MOS transistors.

The surfaces of the gate electrodes 111 and 112 of the aforementionedtransfer MOS transistors, the portions of the gate electrodes 114 of theaforementioned drive MOS transistors, and the entire and portions of thesurfaces of the aforementioned heavily doped n-type impurity regions 102and 103 and the aforementioned heavily doped p-type impurity region 110are formed with the titanium silicide film 142 having a thickness of 50nm to have their resistances lowered by the so-called “silicifyingtechnique”. Moreover, the local wiring lines are formed of a compositefilm (or a poly-cide film) composed of a polycrystalline silicon film162 and the overlying titanium silicide film 142 and formed by theaforementioned silicifying step, and the titanium silicide films 142overlying the heavily doped n-type impurity region 102 and the heavilydoped p-type impurity region 110 are automatically connected with eachother through the titanium silicide film 142 formed over theaforementioned polycrystalline silicon film 162. Incidentally, themethods of Embodiments 3 to 5 can be applied to that for connecting thelocal wiring lines and the silicon substrate and the gate electrodes.Moreover, the present embodiment can also be applied to the structurefor forming the capacity element C₁ of Embodiment 6. At this time,moreover, the aforementioned polycrystalline silicon film 162 maypreferably be doped with an impurity. Especially, boron has a lowerdiffusion rate in the titanium silicide than arsenic or phosphor so thatit can suppress the increase in the contact resistance between theheavily doped impurity region in the silicon substrate and the localwiring lines. In this case, the impurity boron can be added immediatelyafter the deposition of the polycrystalline silicon film 162 by the ionimplantation for implanting the ions of BF₂ by an acceleration energy of25 KeV and in a dosage of 5×10¹⁵ atoms/cm². Incidentally, thisactivation of the impurity can effect the thermal step for forming thesilicide layer.

Moreover, the polycrystalline silicon film 162 may have its insidedivided into the region to be doped with an n-type impurity and theregion to be dope with a p-type impurity. This method may be effected bythe ion implantation using a photoresist as the mask. Incidentally, inthis case, it is desired that the heavily doped n-type impurity regionin the silicon substrate is connected with the polycrystalline siliconfilm 162 doped with the n-type impurity whereas the heavily doped p-typeimpurity region in the silicon substrate is connected with thepolycrystalline silicon film 162 doped with the p-type impurity.

In the method of fabricating the aforementioned local wiring lines, apolycrystalline silicon film having a thickness of about 150 nm may beused in place of the amorphous silicon film 141 at the time of formingthe amorphous silicon film 145 of Embodiment 2, as shown in FIG. 48( a).In the present embodiment, moreover, the material for the silicifyingreaction is exemplified by titanium but can be replaced by a compound ofa well-known refractory metal and silicon, such as cobalt silicide,platinum silicide, nickel silicide, tungsten silicide or tantalumsilicide. An alternative material may be a composite film of theaforementioned refractory metal and the polycrystalline silicon film.

According to the present embodiment, the mechanical stress to be appliedto the underlying silicon oxide film 141 when the titanium silicide ofthe local wiring lines is to be formed can be damped by theaforementioned polycrystalline silicon film 162, to prevent thedielectric breakdown and the leakage current increase of the siliconoxide film 141. Especially in case the present embodiment is applied tothe formation of the capacity element C₁ of Embodiment 6, it is possibleto provide a highly reliable SRAM.

Embodiment 9

The present embodiment relates to a method of forming the local wiringlines. FIG. 58 presents a top plan view of the present embodiment. InFIG. 58, the local wiring lines 119 and 120 are partially formed withregions 163 heavily doped with oxygen. The oxygen doping method may beexemplified by the well-known method such as the ion implantation. Theregions heavily doped with the oxygen act to suppress the mutualdiffusions of the n-type impurity and the p-type impurity in the localwiring lines. Incidentally, the structure of FIG. 58 of the portionsother than the local wiring lines is similar to that of Embodiment 2, asshown in FIG. 44, and its repeated description will be omitted.

According to the present embodiment, it is possible to suppress theincrease in the contact resistance between the heavily doped impurityregions in the silicon substrate and the local wiring lines and thefluctuation of the characteristics and the dispersion of the thresholdvoltage or the drain current of the drive MOS transistors.

Embodiment 10

The present embodiment relates to the aluminum wiring lines in the SRAMmemory cell in Embodiment 2. FIG. 59 is a top plan view of the SRAM cellaccording to the present embodiment and shows a portion of the aluminumwiring lines. The portion of the MOS transistors is absolutely similarto that of Embodiment 2. In FIG. 59, a first-layered aluminum electrode164 is formed between the first-layered aluminum electrode 129 of theground wiring line and the first-layered aluminum electrode 130 of thesupply wiring line. This aluminum electrode 164 shorts the word lineswhich are divided for the individual memory mats.

According to the present embodiment, the word lines can have theirresistances substantially lowered to provide a high speed SRAM.

Embodiment 11

The present embodiment relates to a semiconductor integrated circuitdevice in which a SRAM using the CMOS transistors of Embodiment 2 andbipolar transistors are formed over a common semiconductor substrate.FIGS. 60( a) to 60(c) and FIGS. 61( a) to 61(c) present sections ofmanufacture steps of the present embodiment and show the portions of thebipolar elements and the CMOS transistors but not the portion of thememory cell of the SRAM. The present embodiment will be described in theorder of the manufacture steps with reference to FIGS. 60( a) to 60(c)and FIGS. 61( a) to 61(c).

First of all, as shown in FIG. 60( a), by using the well-knownself-alignment technique, a p-type silicon substrate 165 is formed withan n-type buried layer 166 by the diffusion of antimony (Sb) and with ap-type buried layer 167 by the ion implantation of boron (B) and by theannealing. The antimony diffusing conditions are properly effected at1,175° C. for about 30 minutes, and the boron ion implanting conditionsare properly effected with an acceleration energy of 50 KeV and in adosage of 7×10¹² atoms/cm². Next, the silicon layer formed to have athickness of 1 μm by the epitaxial growth is formed therein with then-well 136 and the p-well 137 and further with the field oxide film 138having a thickness of 400 nm. Incidentally, the n-well 136 and thep-well 137 are formed over the n-type buried layer 166 and the p-typeburied layer 167, respectively, by a method similar to that ofEmbodiment 2.

Next, as shown in FIG. 60( b), the gate oxide film 139 having athickness of 10 nm is formed as in Embodiment 2. After this, thepolycrystalline silicon film having a thickness of 200 nm is depositedby the LPCVD method to pattern gate electrodes 172. Next, a photoresistis used as the mask to implant phosphor (P) thereby to form a collectorlead-out portion 168 of the bipolar. Likewise, by the ion implantationof arsenic (As), a heavily doped n-type impurity region 170 is formed onthe source/drain of the n-channel MOS transistors and on the collectorportion of the bipolar. Likewise, a heavily doped p-type impurity region171 of the source/drain portions of the p-channel MOS transistors and aheavily doped p-type impurity region 169 of the base lead-out portion ofthe bipolar transistors are simultaneously formed by the ionimplantation of BF₂. These ion implantation conditions may be identicalto those of Embodiment 2.

Next, as shown in FIG. 60( c), the portions to form the bases of thebipolar transistors are formed with p-type impurity regions 173 by theboron ion implantation using a photoresist as the mask and by apredetermined annealing treatment. The ion implantation conditions arean acceleration energy of 50 KeV and a dosage of 2×10¹⁴ atoms/cm² forthe ion implantation of BF₂. Subsequently, the silicon oxide film 141having a thickness of 50 nm is deposited by the LPCVD method and is thenremoved from the portions to form the emitters of the bipolartransistors by the dry etching method using the photoresist mask.

Next, as shown in FIG. 61( a), the polycrystalline silicon film 162having a thickness of 200 nm is deposited by the LPCVD method and hasits resistance lowered by the arsenic ion implantation and by apredetermined annealing treatment to form a heavily doped n-typeimpurity region 174 for the emitter layer. The ion implantationconditions may be exemplified by the implantation energy of 80 KeV and adosage of 1×10¹⁶ atoms/cm². Moreover, the polycrystalline silicon film162 is patterned into the shape of the emitter electrodes by thephotolithography, and the silicification is the carried out by using thephotoresist 146 as the mask to etch off the silicon oxide film 141thereby to expose the silicon substrate and the gate electrodes to theoutside.

Next, as shown in FIG. 61( b), the silicon substrate and gate electrodesthus exposed and the emitter electrodes are silicified to form thetitanium silicide film 142 as in Embodiment 1.

The subsequent wiring steps can be similar to those of Embodiment 2 (asshown in FIG. 61( c)). Incidentally, the present embodiment has beendescribed while premising the local wiring lines using the titaniumsilicide. However, the resistance lowering material can be exemplifiednot only by the titanium silicide but also by a refractory metal such ascobalt, tantalum, nickel, tungsten or platinum, or its compound (i.e.,silicide) with silicon.

According to the present embodiment, it is possible to simultaneouslyform the highly integrated SRAM memory cell having the local wiringlines of the laminated structure using the silicification, the bipolarelements and the CMOS transistors, thereby to provide a SRAM capable ofoperating at a high speed.

Embodiment 12

The present embodiment relates to a semiconductor integrated circuitdevice in which a SRAM using the CMOS transistors of Embodiment 11 andbipolar transistors are formed on a common semiconductor substrate, andto a method of forming no silicide layer over the emitter electrodes.FIG. 62 presents a section of the present embodiment and shows theportions of the bipolar elements and the CMOS transistors but not theportion of the memory cell of the SRAM. In FIG. 62, over thepolycrystalline silicon film 162 of the emitter electrodes, there isformed a silicon oxide film 176 but not the silicide film 142.

The process for manufacturing the aforementioned bipolar transistorswill be described in the following with reference to the manufactureprocess, as described in connection with Embodiment 11. First of all,when the polycrystalline silicon film 162 of the emitters is to bepatterned (as corresponds to the step of Embodiment 11, as shown in FIG.61( a)), the silicon oxide film 176 having a thickness of 80 nm isdeposited on the polycrystalline silicon film 162 and is patterned intothe shape of the emitter electrodes. After this, the silicon oxide film176 is sued as the dry etching mask to pattern the polycrystallinesilicon film 162. Next, at the step of exposing the silicon substrate orthe gate electrodes for the silicification, the silicon oxide film 141is dry-etching with the photoresist pattern (as shown in FIG. 61( a))covering the aforementioned emitter electrodes. The subsequentsilicifying step and the aluminum wiring line forming step are similarto those of Embodiment 11.

Incidentally, the polycrystalline silicon film 162 of the presentembodiment forms the emitter electrodes but can be used in otherportions to form resistance elements.

According to the present embodiment, the polycrystalline silicon film ofthe emitter electrodes of the bipolar transistors is not silicified sothat no influence is exerted upon the diffusion of the impurity into thesilicide film thereby to easily control the impurity distribution of theheavily doped n-type impurity region of the emitters into the siliconsubstrate. As a result, it is possible to provide bipolar transistorswhich has a high current gain and a high performance.

Embodiment 13

The present embodiment relates to a semiconductor integrated circuitdevice, in which a SRAM having the CMOS transistors or Embodiment 11 andthe bipolar transistors are formed on a common semiconductor substrate,and to a structure using the local wiring lines as the lead-outelectrodes of the base. FIG. 63 presents a section of the presentembodiment and shows the portions of the bipolar elements and the CMOStransistors but not the portion of the memory cells of the SRAM. In FIG.63, the heavily doped p-type impurity region 169 of the base regions ofthe bipolar transistors, the polycrystalline silicon film 162 formingthe local wiring lines common to the emitter electrodes, and the heavilydoped n-type impurity region 170 of the MOS transistors are connectedwith each other through the titanium silicide film 142, and thistitanium silicide film 142 is formed over the polycrystalline siliconfilm 162. As shown in FIG. 63, moreover, the titanium silicide film 142overlying the aforementioned polycrystalline silicon film 162 can beformed thereover with openings to connect aluminum wiring lines 175.Incidentally, in the present embodiment, the local wiring lines areconnected with the n-channel source/drain but can be connected with thep-channel source/drain. Moreover, the present embodiment can also beapplied to Embodiment 12 to omit the silicification of the emitterelectrodes.

According to the present embodiment, the area required for effectingcontacts between the bases of the bipolar transistors and thesource/drain of the MOS transistors can be made smaller than that of theordinary one, to provide a highly integrated SRAM and a high speed SRAM.

Embodiment 14

The present embodiment relates to a structure using the titanium nitridefilm in the local wiring lines. FIGS. 64( a) and 64(b) and FIGS. 65( a)and 65(b) present sections showing the manufacture steps of the presentembodiment. The manufacture process of the present embodiment will bedescribed in the following with reference to the Figures. First of all,the steps when and before the silicon substrate is formed with the MOStransistors and has the silicon oxide film 141 deposited thereon, aresimilar to those of Embodiment 2, as shown in FIG. 47( c). Next, thephotoresist 146 is used as the mask to form the openings in theaforementioned silicon oxide film 141 thereby to expose the siliconsubstrate and the gate electrodes to the outside (as shown in FIG. 64(a)). Next, a titanium film 177 having a thickness of 50 nm is depositedall over the surface by the sputtering method (as shown) in FIG. 64(b)). Then, an annealing treatment is executed in the nitrogen atmosphereof 675° C. for 30 minutes, to change the surface of the titanium film177 into a titanium nitride film 178 and to form a titanium silicidefilm 179 over the heavily doped n-type impurity regions 102 and 103 andthe heavily doped p-type impurity region 110 over the silicon substrate,and over the gate electrodes 111, 112, 113 and 114. Next, thephotoresist 146 is used as the mask to remove the unnecessary portionsof the titanium nitride film 178 and the unreacted titanium film by thedry etching method and by the wet etching method using an aqueoussolution of hydrogen peroxide. Incidentally, the temperature and timeperiod for the aforementioned annealing treatment are adjusted to setthe thicknesses of the titanium silicide film and the titanium nitridefilm to desired values. Next, an annealing treatment is carried out inthe nitrogen atmosphere of 800° C. to lower the resistances of thetitanium nitride film 178 and the titanium silicide film 179 (as shownin FIG. 65( a)).

The subsequent steps of forming the aluminum wiring lines are similar tothose of Embodiment 2 (as shown in FIG. 65( b)).

According to the present embodiment, the local wiring lines of the SRAMmemory cell can be formed of the titanium nitride film acting as thebarrier against the diffusion of the impurity. As a result, it ispossible to eliminate the problem which might otherwise be caused by thediffusion of the impurity of the heavily doped impurity regions of then-channel MOS transistors and the p-channel MOS transistors into thesilicide thereby to increase the contact resistance in the boundary ofthe silicon substrate.

Embodiment 15

The present embodiment relates to a capacity element which is formed inthe circuit element group using the CMIS transistors in the periphery ofthe portion other than the memory cell. FIG. 66 presents a sectionalstructure of the present embodiment. In FIG. 66, the n-type siliconsubstrate 135 is formed with the n-type well 137, the field oxide film138, the gate oxide film 139 and a gate electrode 1124. This gateelectrode 1124 is used as the mask for an ion implantation to form aheavily doped n-type impurity region 1225 simultaneously with thesource/drain region of the MIS transistors. Incidentally, these stepsare similar to those used in the ordinary CMIS process, as has beendescribed in connection with Embodiment 2. Moreover, the gate electrode1124 is formed thereover though a silicon oxide film 1126 with atitanium silicide film 1127 for the local wiring lines, and thistitanium silicide film 1127 has its one end connected with the heavilydoped n-type impurity region 1125. The aforementioned gate electrode isconnected with aluminum wiring lines 1128.

Thanks to the structure described above, a MIS capacity is formedbetween the gate electrode 1124 and the n-type well 137, and a capacityelement is formed between the gate electrode 1124 and the titaniumsilicide film 1127 for the local wiring lines. Incidentally, the presentembodiment uses the titanium silicide film is used for the local wiringlines, but the poly-cide structure can also be adopted by applyingEmbodiment 8. Moreover, the present embodiment is described inconnection with the MIS capacity of the n-type well, but the conductiontype of the impurity may be inverted in connection with the MIS capacityof the p-type well. Incidentally, the capacity element made in thepresent embodiment can be applied to a circuit for raising or loweringthe supply voltage.

According to the present embodiment, no step is added except for thestep of manufacturing the memory cell according to the presentinvention, and the two capacity elements can be formed withoutincreasing the necessary area on the silicon substrate. As a result, itis possible to provide the capacity element C₁ requiring a small area.

Embodiment 16

The present embodiment relates to a resistance element which is formedin the circuit element group using the CMIS transistors in the peripheryof the portion other than the memory cell. FIG. 67 presents a sectionalstructure of the present embodiment. In FIG. 67, the n-type siliconsubstrate 135 is formed with the p-type well 1336 and the field oxidefilm 138, and the heavily doped n-type impurity region 1125 is formedsimultaneously with the source/drain regions of the MIS transistors andis overlaid by the silicon oxide film 1126. Incidentally, these stepsare similar to those of the ordinary CMIS process which has beendescribed in connection with Embodiment 2. At the portions to beconnected with the aluminum wiring lines 1128, moreover, the siliconoxide film 1126 is selectively etched to form the titanium silicide film1127 in the portion over the heavily doped impurity region 1125 at thesilicifying step.

Thanks to the aforementioned structure, the heavily doped impurityregion 1125 presents the resistance element. Incidentally, theresistance element thus formed in the present embodiment can be used inan input protecting circuit, for example.

According to the present embodiment, no step is added except for thestep of manufacturing the memory cell according to the presentinvention, and the resistance element can be formed without increasingthe necessary area on the silicon substrate.

Embodiment 17

The present embodiment relates to a method for connecting the localwiring lines and the silicon substrate. FIG. 68 presents a sectionalstructure of the SRAM memory cell according to the present embodimentand shows the portion of the local wiring lines of the section, as takenalong line A-A′ of FIG. 49( a), in an enlarged scale. The steps when andbefore the MIS transistors are formed on the silicon substrate, aresimilar to those at and before FIG. 48( c) of Embodiment 2. In FIG. 48(c), the titanium nitride film 178, which is formed simultaneously as thepolycrystalline silicon film 145 is silicified, is patterned by usingthe photography similar to that described in connection with Embodiment14, to leave a desired portion, and the heavily doped n-type impurityregion 102 and the titanium silicide film 141 are connected through thattitanium nitride film 178 (as shown in FIG. 68). The subsequent stepsmay be similar to those of Embodiment 2, as shown in FIG. 49( b).

According to the present embodiment, the silicon substrate and the gateelectrodes and the local wiring lines can be easily connected.

According to Embodiments 2 to 17, the source/drain and gate electrodesof the MIS transistors can have their individual surfaces formed withthe low resistance material by the silicifying process, and the localwiring lines can be laminated over the gate electrodes. As a result, itis possible to provide a semiconductor integrated circuit device havingthe complete CMOS type SRAM cell which has a high integration, aresistance to the soft error and an excellent consistency with the logicprocess.

Although our invention has been specifically described in connectionwith Embodiments 2 to 17, it should not be limited thereto but cannaturally be modified in various manners without departing from the gistthereof. Over the local wiring lines 119, 120, 153 and 154 according toEmbodiments 2 to 17, for example, there may be arranged the referencevoltage line 20 according to Embodiment 1. The capacity element C₂ maybe formed between the local wiring lines 119, 120, 153 and 154 and thereference voltage line 20. These modifications can also achieve the sameeffects as these of Embodiment 1.

The representative ones of the invention to be disclosed in Embodiments2 to 17 will be summarized in the following.

-   (1) In a semiconductor integrated circuit device with a plurality of    insulated gate type field effect transistors comprising: a first    impurity region 102, 105, 108 and 110 formed over the surface of a    semiconductor substrate; and a first conducting film 111 and a    second conducting film 113 and 114 formed through a first insulating    film 139 and in the same layer,

a semiconductor integrated circuit device and a process formanufacturing the same, wherein a third conducting film 142 having alower resistance than the first impurity region 102, 105, 108 and 110 orthe second conducting film 113 and 114 is formed over a portion of thefirst impurity region and the first conducting film, and wherein thethird conducting film 143 has a lower resistance than that of the firstconducting film 111.

-   (2) In a semiconductor integrated circuit device comprising: with a    first impurity region formed over the surface of a semiconductor    substrate; a first conducting film 111 and a second conducting film    113 and 114 formed through a first insulating film 139 and in the    same layer; and a plurality of fourth conducting films 119, 120,    142, 151 and 152 formed over the second conducting film 113 and 114    through a second insulating film 141 and 150,

a semiconductor integrated circuit device and a process formanufacturing the same as set forth in (1), wherein the fourthconducting films 119, 120, 142, 151 and 152 are so formed through thesecond if 141 and 150 that at least their portions are superposed overthe second conducting film 113 and 114, wherein the first conductingfilm 111 and a portion other than the superposed portion of the firstimpurity region 102, 105, 108 and 110 and the second conducting film 113and 114 over the fourth conducting films 119, 120, 142, 151 and 152 areformed with a third conducting film 142 having a lower resistance thanthat of the first impurity region or the first conducting film, whereinthe first conducting film 111 has a lower resistance than that of thesecond conducting film 113 and 114, wherein the fourth conducting films119, 120, 142, 151 and 152 are formed by the method having the means forforming the third conducting film 142, and wherein the other secondconducting film 113 and 114 is connected with the fourth conductingfilms 119, 120, 142, 151 and 152.

-   (3) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth in (2), comprising: the step of    forming the first impurity region 102, 105, 108 and 110 on the    surface of the semiconductor substrate; the step of forming the    first insulating film 139; the step of forming the first and second    conducting films 111, 113 and 114; the step of the second insulating    film 141 and 150 on the first and second conducting films; the step    of forming a fifth conducting film 145; the step of simultaneously    forming an opening 118 to the first conducting film 111 and an    opening 115, 116 and 117 to the first impurity region 102, 105, 108    and 110 to cover the fifth conducting film and removing the second    insulating film; the step of lowering the resistance of the fifth    conducting film and then selectively forming the conducting film 142    partially in the portions of the first conducting film 111 exposed    to the opening and the first impurity region 102, 105, 108 and 110    in self-alignment; and the step of the third conducting film 142 in    that portions with the first impurity region 102, 105, 108 and 110    and the fourth conducting films 119, 120, 142, 151 and 152.-   (4) In a static type random access memory comprising: a flip-flop    circuit having a first storage node and a second storage node    crossly connecting one and other drains of a pair of drive insulated    gate type field effect transistors Qd₁ and Qd₂; a pair of transfer    insulated gate type field effect transistors Qt₁ and Qt₂    individually connected with the first and second storage node, and a    pair of load elements Qp₁ and Qp₂; and word lines having the gate    electrode of the transfer insulated gate type field effect    transistors,

a semiconductor integrated circuit device and a process formanufacturing the same, wherein the drive insulated gate type fieldeffect transistors and the transfer insulated gate type field effecttransistors have their gate insulating films formed of the firstinsulating film 139, and wherein the transfer insulated gate type fieldeffect transistors have their gate electrodes 111 and 142 given a lowerresistance than that of the gate electrodes 113 and 114 of the driveinsulated gate type field effect transistors.

-   (5) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth in (1) and (4), wherein the    drive insulated gate type field effect transistors Qd₁ and Qd₂ and    the load insulated gate type field effect transistors Qp₁ and Qp₂ of    a memory cell group have their gate electrodes formed of the second    conducting film 113 and 114, and wherein the transfer insulated gate    type field effect transistor or the memory cell group and the    insulated gate type field effect transistors of a peripheral circuit    group have their gate electrodes formed of a composite film composed    of the first conducting film 111 and the third conducting film 142    having a lower resistance than that of the first conducting film.-   (6) In a static type random access memory wherein a pair of transfer    MIS transistors Qt₁ and Qt₂, a pair of load MIS transistors Qp₁ and    Qp₂ and a pair of drive MIS transistors Qd₁ and Qd₂ are individually    arranged in an X direction, and wherein the transfer MIS transistors    have their gate electrode 111 extended in the X direction whereas    the drive MIS transistors and the load MIS transistors have their    common gate electrodes 113 and 114 extended in a Y direction,

a semiconductor integrated circuit device and a process formanufacturing the same, wherein a pair of local wiring lines 119, 120,142, 151 and 152 are individually extended in the Y direction over thecommon gate electrodes 113 and 114 of the drive MIS transistors and theload MIS transistor, wherein by using individual identical connectionmeans 142, one 119 and 151 of the paired local wiring lines is connectedat the side wall of the end portion with the heavily doped n-typeimpurity region 102 of the drain of one drive MIS transistor Qd₁ whereasthe other 120 and 152 of the paired local wiring lines is connected atthe side wall of the end portion with the heavily doped n-type impurityregion 103 of the drain of the other drive MIS transistor Qd₂, whereinone 119 and 151 of the paired local wiring lines is connected at theside wall of the end portion with the gate electrode 114 of the otherdrive MIS transistor whereas the other 120 and 152 of the paired localwiring lines is connected at the side wall of the end portion with thegate electrode 113 of the one drive MIS transistor.

-   (7) In a semiconductor integrated circuit device comprising: a first    impurity region 102, 105, 108 and 110 formed over the surface of the    semiconductor substrate; a first conducting film 111 and a pair of    second conducting films 113 and 114 formed through a first    insulating film and in the same layer; and a pair of fourth    conducting films 119, 120, 141, 153 and 154 formed over the second    conducting films through a second insulating film 141 and 150,    wherein the paired transfer insulated gate type field effect    transistors have their gate electrodes formed of the first    conducting film 111, wherein the paired drive insulated gate type    field effect transistors have their gate electrodes formed of the    second conducting films 113 and 114, and wherein the first or second    storage node contains at least the first impurity region.

a semiconductor integrated circuit device and a process formanufacturing the same as set forth in (5) or (6), wherein said fourthconducting films 119, 120, 142, 153 and 154 are so formed through thesecond insulating film 141 and 150 that at least their portions aresuperposed over the second conducting films 113 and 114, wherein thefirst conducting film 111 and a portion other than the superposedportion of the first impurity region 102, 105, 108 and 110 and thesecond conducting films 113 and 114 over the fourth conducting films119, 120, 142, 153 and 154 are formed with a third conducting film 142having a lower resistance than that of the first impurity region 102,105, 108 and 110 or the second conducting films 113 and 114, and whereinone of the fourth conducting films 119, 120, 142, 153 and 154 isinsulated from the gate electrode of one drive insulated gate type fieldeffect transistor but is connected with the gate electrode of the otherdrive insulated gate type field effect transistor to effect the localinter-connection in the memory cell.

-   (8) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth in (7), wherein the paired load    elements are composed of the drive insulated gate type field effect    transistors Qd₁ and Qd₂ and the paired of load insulated gate type    field effect transistors Qp₁ and Qp₂ of the opposite conduction    type, wherein the load insulated gate type field effect transistors    and the drive insulated gate type field effect transistors connected    with the common storage node are formed of the common gate electrode    113 and 114, and wherein the drains of the drive and load insulated    gate type field effect transistors connected with one storage node    and the gate electrodes of the drive and load insulated gate type    field effect transistors connected with the other storage node are    connected with each other through the fourth conducting films 119,    120, 142, 153 and 154 to form the cross connections of the flip-flop    circuit.-   (9) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth in (2) and (7), wherein the    portions in the first conducting film 111, the second conducting    films 113 and 114 and the first impurity region 102, 105, 108 and    110 other than those superposed over the fourth conducting films are    formed with the third conducting film 142 having a lower resistance    by using the fourth conducting films as the mask.-   (10) A semiconductor integrated circuit device and a process for    manufacturing the same, wherein the first and second conducting    films 111, 113 and 114 are made of polycrystalline silicon doped    with an impurity, and wherein the third conducting film 142 is made    of a compound of a refractory metal such as W, Ti, Co, Pt, Ni or Ta    and silicon.-   (11) A semiconductor integrated circuit device and a process for    manufacturing the same, wherein the second conducting films 113 and    114, the second insulating film 141 and 150 and the fourth    conducting films 119, 120, 142, 153 and 154 form a capacity element    C₁ for supplying electric charge to the second conducting films.-   (12) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth in (11), wherein the capacity    element C₁ is connected between the first and second storage nodes.-   (13) A semiconductor integrated circuit device and a process for    manufacturing the same, wherein the second insulating film 141 and    150 contains a silicon nitride film.-   (14) In a semiconductor integrated circuit device, in which having    bipolar transistors and insulated gate type field effect transistors    are formed over a common semiconductor substrate.

a semiconductor integrated circuit device and a process formanufacturing the same as set forth in (2) and (7), wherein the bipolartransistors have their emitter electrodes formed of the fourthconducting films 142.

-   (15) In a semiconductor integrated circuit device,

a semiconductor integrated circuit device and a process formanufacturing the same as set forth in (5) to (7), wherein a powerwiring line for supplying the electric power to the static type randomaccess memory cell array and a ground wiring line are composed offirst-layered aluminum wiring lines 129 and 130, wherein data lines arecomposed of second-layered aluminum wiring lines 133 and 134, andwherein a logic circuit other than the memory cell array is made ofthree layers or more aluminum wiring lines.

-   (16) A semiconductor integrated circuit device and a process for    manufacturing the same as set forth (15), wherein the first-layered    aluminum wiring lines 164 are formed in the direction of the word    lines to connect a plurality of word lines at the extensions of the    former word lines.-   (17) In a semiconductor integrated circuit device in which a static    type random access memory and the logic element of a microprocessor    are formed over a common semiconductor substrate,

a semiconductor integrated circuit device and a process formanufacturing the same as set forth in (5) to (7), wherein the insulatedgate type field effect transistors of the logic element group have theirgate electrodes formed of a composite film composed of the firstconducting film 111 and the third conducting film 142.

1. A semiconductor integrated circuit device comprising: a memory cellof a static random access memory including a first n-channel MISFET, asecond n-channel MISFET, a first p-channel MISFET and a second p-channelMISFET, each of the first-channel MISFET and the second n-channel MISFEThaving a gate electrode formed over a semiconductor substrate, and asource region and a drain region formed in the semiconductor substrate,each of the first p-channel MISFET and the second p-channel MISFEThaving a gate electrode formed over the semiconductor substrate, and asource region and a drain region formed in the semiconductor substrate;a first insulating film formed over the MISFETs; a first conductive filmand a second conductive film formed on the first insulating film andcomprised of a different conductive layer from that of the gateelectrodes of the MISFETs, the first conductive film being electricallyconnected to the drain region of the first n-channel MISFET, the drainregion of the first p-channel MISFET, the gate electrode of the secondn-channel MISFET and the gate electrode of the second p-channel MISFET,the second conductive film being electrically connected to the drainregion of the second n-channel MISFET, the drain region of the secondp-channel MISFET, the gate electrode of the first n-channel MISFET andthe gate electrode of the first p-channel MISFET; a third conductivefilm, a fourth conductive film, a fifth conductive film and a sixthconductive film formed with the same level layer as the first conductivefilm and the second conductive film and arranged separately with eachother; a second insulating film formed over the first conductive film,the second conductive film, the third conductive film, the fourthconductive film, the fifth conductive film and the sixth conductivefilm; a power source line formed over the second insulating film andelectrically connected to the source region of the first p-channelMISFET through the third conductive film and to the source region of thesecond p-channel MISFET through the fourth conductive film; and areference voltage line formed over the second insulating film, formedwith the same level layer as the power source line and electricallyconnected to the source region of the first n-channel MISFET through thefifth conductive film and to the source region of the second n-channelMISFET through the sixth conductive film.
 2. A semiconductor integratedcircuit device according to claim 1, further comprising: a wiring lineformed over the second insulating film and formed with the same levellayer as the power source line, wherein the memory cell includes a firsttransfer MISFET and a second transfer MISFET each having a gateelectrode, and wherein the wiring line is electrically connected to thegate electrodes of the first transfer MISFET and the second transferMISFET.
 3. A semiconductor integrated circuit device according to claim1, wherein the power source line and the reference voltage line extendover the first conductive film and the second conductive film.
 4. Asemiconductor integrated circuit device according to claim 1, whereinthe p-channel MISFETs are arranged to be spaced from the n-channelMISFETs in a first direction, and wherein the power source line and thereference voltage line extend in a second direction crossing the firstdirection.
 5. A semiconductor integrated circuit device according toclaim 1, further comprising: a logic element of a microprocessor.
 6. Asemiconductor integrated circuit device according to claim 1, whereineach of the source region and the drain region of the p-channel MISFETincludes a selectively formed region such that a silicide layer isformed on the selectively formed region.
 7. A semiconductor integratedcircuit device according to claim 1, wherein a surface of the secondinsulating film is substantially flat.
 8. A semiconductor integratedcircuit device comprising: a memory cell of a static random accessmemory including a first n-channel MISFET, a second n-channel MISFET, afirst p-channel MISFET and a second p-channel MISFET, each of the firstn-channel MISFET and the second n-channel MISFET having a gate electrodeformed over a semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate, each of the firstp-channel MISFET and the second p-channel MISFET having a gate electrodeformed over the semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate; a first insulating filmformed over the MISFETs; a first conductive film and a second conductivefilm formed on the first insulating film and comprised of a differentconductive layer from that of the gate electrodes of the MISFETs, thefirst conductive film being electrically connected to the drain regionof the first n-channel MISFET, the drain region of the first p-channelMISFET, the gate electrode of the second n-channel MISFET and the gateelectrode of the second p-channel MISFET, the second first conductivefilm being electrically connected to the drain region of the secondn-channel MISFET, the drain region of the second p-channel MISFET, thegate electrode of the first n-channel MISFET and the gate electrode ofthe first p-channel MISFET; a third conductive film, a fourth conductivefilm, a fifth conductive film and a sixth conductive film formed withthe same level layer as the first conductive film and the secondconductive film and arranged separately with each other, the firstp-channel MISFET being arranged to be spaced from the first n-channelMISFET in a first direction, the second n-channel MISFET being arrangedto be spaced from the second p-channel MISFET in the first direction,the fourth conductive film arranged to be spaced from the thirdconductive film in a second direction crossing the first direction, andthe sixth conductive film arranged to be spaced from the fifthconductive film in the second direction; a second insulating film formedover the first conductive film, the second conductive film, the thirdconductive film, the fourth conductive film the fifth conductive filmand the sixth conductive film; a power source line formed over thesecond insulating film and electrically connected to the source regionof the first p-channel MISFET through the third conductive film and tothe source region of the second p-channel MISFET through the fourthconductive film; and a reference voltage line formed over the secondinsulating film, formed with the same level layer as the power sourceline and electrically connected to the source region of the firstn-channel MISFET through the fifth conductive film and to the sourceregion of the second n-channel MISFET through the sixth conductive film,the power source line and the reference voltage line extending in thesecond direction.
 9. A semiconductor integrated circuit device accordingto claim 8, further comprising: a wiring line formed over the secondinsulating film and formed with the same level layer as the power sourceline, wherein the memory cell includes a first transfer MISFET and asecond transfer MISFET each having a gate electrode, and wherein thewiring line is electrically connected to the gate electrodes of thefirst transfer MISFET and the second transfer MISFET.
 10. Asemiconductor integrated circuit device according to claim 8, whereinthe power source line and the reference voltage line extend over thefirst conductive film and the second conductive film.
 11. Asemiconductor integrated circuit device according to claim 8, furthercomprising: a logic element of a microprocessor.
 12. A semiconductorintegrated circuit device according to claim 8, wherein each of thesource region and the drain region of the p-channel MISFETs includes aselectively formed region such that a silicide layer is formed on theselectively formed region.
 13. A semiconductor integrated circuit deviceaccording to claim 8, wherein a surface of the second insulating film issubstantially flat.
 14. A semiconductor integrated circuit devicecomprising: memory cells of a static random access memory, eachincluding a first n-channel MISFET, a second n-channel MISFET, a firstp-channel MISFET and a second p-channel MISFET, each of the firstn-channel MISFET and the second n-channel MISFET having a gate electrodeformed over a semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate, each of the firstp-channel MISFET and the second p-channel MISFET having a gate electrodeformed over the semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate; a first insulating filmformed over the MISFETs; first conductive films and second conductivefilms formed on the first insulating film and comprised of a differentconductive layer from the gate electrodes of the MISFETs, each of thefirst conductive films, in the memory cell, being electrically connectedto the drain region of the first n-channel MISFET, the drain region ofthe first p-channel MISFET, the gate electrode of the second n-channelMISFET and the gate electrode of the second p-channel MISFET, each ofthe second conductive films, in the memory cell, being electricallyconnected to the drain region of the second n-channel MISFET, the drainregion of the second p-channel MISFET, the gate electrode of the firstn-channel MISFET and the gate electrode of the first p-channel MISFET;third conductive films, fourth conductive films, fifth conductive filmsand sixth conductive films formed with the same level layer as the firstconductive films and the second conductive films such that, in thememory cell, the third conductive films, the fourth conductive films,the fifth conductive films and the sixth conductive films are arrangedseparately with each other; a second insulating film formed over thefirst conductive films, the second conductive films, the thirdconductive films, the fourth conductive films, the fifth conductivefilms and the sixth conductive films; power source lines formed over thesecond insulating film and electrically connected to the source regionsof the first p-channel MISFETs through the third conductive films and tothe source regions of the second p-channel MISFETs through the fourthconductive films; and reference voltage lines formed over the secondinsulating film, formed with the same level layer as the power sourcelines and electrically connected to the source regions of the firstn-channel MISFETs through the fifth conductive films and to the sourceregions of the second n-channel MISFETs through the sixth conductivefilms.
 15. A semiconductor integrated circuit device according to claim14, further comprising: wiring lines formed over the second insulatingfilm and formed with the same level layer as the power source lines,wherein the memory cell includes a first transfer MISFET and a secondtransfer MISFET each having a gate electrode, and wherein the wiringlines are electrically connected to the gate electrodes of the firsttransfer MISFETs and the second transfer MISFETs.
 16. A semiconductorintegrated circuit device according to claim 14, wherein, in the memorycell, the power source lines and the reference voltage lines extend overthe first conductive films and the second conductive films.
 17. Asemiconductor integrated circuit device according to claim 14, wherein,in the memory cell, the p-channel MISFETs are arranged to be spaced fromthe n-channel MISFETs in a first direction, and wherein, in the memorycell, the power source lines and the reference voltage lines extend in asecond direction crossing the first direction.
 18. A semiconductorintegrated circuit device according to claim 14, further comprising: alogic element of a microprocessor.
 19. A semiconductor integratedcircuit device according to claim 14, wherein each of the source regionand the drain region of the p-channel MISFETs includes a selectivelyformed region such that a silicide layer is formed on the selectivelyformed region.
 20. A semiconductor integrated circuit device accordingto claim 14, wherein a surface of the second insulating film issubstantially flat.
 21. A semiconductor integrated circuit devicecomprising: memory cells of a static random access memory, eachincluding a first n-channel MISFET, a second n-channel MISFET, a firstp-channel MISFET and a second p-channel MISFET, each of the firstn-channel MISFET and the second n-channel MISFET having a gate electrodeformed over a semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate, each of the firstp-channel MISFET and the second p-channel MISFET having a gate electrodeformed over the semiconductor substrate, and a source region and a drainregion formed in the semiconductor substrate; a first insulating filmformed over the MISFETs; first conductive films and second conductivefilms formed on the first insulating film and comprised of a differentconductive layer from the gate electrodes of the MISFETs, the firstconductive films, in the memory cell, being electrically connected tothe drain region of the first n-channel MISFET, the drain region of thefirst p-channel MISFET, the gate electrode of the second n-channelMISFET and the gate electrode of the second p-channel MISFET, the secondfirst conductive films, in the memory cell, being electrically connectedto the drain region of the second n-channel MISFET, the drain region ofthe second p-channel MISFET, the gate electrode of the first n-channelMISFET and the gate electrode of the first p-channel MISFET; thirdconductive films, fourth conductive films, fifth conductive films andsixth conductive films formed with the same level layer as the firstconductive films and the second conductive films such that, in thememory cell, the third conductive films, the fourth conductive films,the fifth conductive films and the sixth conductive films are arrangedseparately with each other, the first p-channel MISFETs being arrangedto be spaced from the first n-channel MISFETs in a first direction, thesecond n-channel MISFETs being arranged to be spaced from the secondp-channel MISFETs in the first direction, the fourth conductive filmsarranged to be spaced from the third conductive films in a seconddirection crossing the first direction, and the sixth conductive filmsarranged to be spaced from the fifth conductive films in the seconddirection; a second insulating film formed over the first conductivefilms, the second conductive films, the third conductive films, thefourth conductive films, the fifth conductive films and the sixthconductive films; power source lines formed over the second insulatingfilm and electrically connected to the source regions of the firstp-channel MISFETs through the third conductive films and to the sourceregions of the second p-channel MISFETs through the fourth conductivefilms; and reference voltage lines formed over the second insulatingfilm, formed with the same level layer as the power source lines andelectrically connected to the source regions of the first n-channelMISFETs through the fifth conductive films and to the source regions ofthe second n-channel MISFETs through the sixth conductive films, thepower source lines and the reference voltage lines extending in thesecond direction.
 22. A semiconductor integrated circuit deviceaccording to claim 21, further comprising: wiring lines formed over thesecond insulating film and formed with the same level layer as the powersource lines, wherein the memory cell includes a first transfer MISFETand a second transfer MISFET, each having a gate electrode, and whereinthe wiring lines are electrically connected to the gate electrodes ofthe first transfer MISFETs and the second transfer MISFETs.
 23. Asemiconductor integrated circuit device according to claim 21, whereinthe power source lines and the reference voltage lines extend over thefirst conductive films and the second conductive films.
 24. Asemiconductor integrated circuit device according to claim 21, furthercomprising: a logic element of a microprocessor.
 25. A semiconductorintegrated circuit device according to claim 21, wherein each of thesource region and the drain region of the p-channel MISFET includes aselectively formed region such that a silicide layer is formed on theselectively formed region.
 26. A semiconductor integrated circuit deviceaccording to claim 21, wherein a surface of the second insulating filmis substantially flat.